Focus adjustment apparatus, imaging apparatus and lens barrel

ABSTRACT

A focus adjustment control apparatus is provided which includes: a focus detection unit that calculates an evaluation value with regard to contrast of an image via an optical system to detect a focus adjustment state of the optical system; an acquisition unit that acquires from a lens barrel at least one of a maximum value and a minimum value of an image plane movement coefficient that represents correspondence relationship between a movement amount of a focus adjustment lens included in the optical system and a movement amount of an image plane; and a control unit that uses at least one of the maximum value and the minimum value of the image plane movement coefficient to determine a drive speed for the focus adjustment lens when the focus detection unit detects the focus adjustment state.

This is a Continuation of International Application No.PCT/JP2012/079189 filed Nov. 9, 2012, which claims the benefit ofJapanese Application No. 2011-247090 filed Nov. 11, 2011. The disclosureof the prior applications is hereby incorporated by reference herein inits entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a focus adjustment apparatus, animaging apparatus and a lens barrel.

2. Description of the Related Art

A technique is heretofore known which calculates an evaluation valuewith regard to the contrast via an optical system while driving a focusadjustment lens at a predetermined drive speed in the optical axisdirection, thereby to detect a focal state of the optical system (referto Patent Literature 1: JP2010-139666A, for example).

Patent Literature 1: JP2010-139666A

SUMMARY OF THE INVENTION

Objects of the present invention include providing a focus adjustmentapparatus which can appropriately detect a focus adjustment state of anoptical system.

The present invention provides the following means to achieve the aboveobjects.

A focus adjustment control apparatus in embodiments is characterized bycomprising: a focus detection unit that calculates an evaluation valuewith regard to contrast of an image via an optical system to detect afocus adjustment state of the optical system; an acquisition unit thatacquires from a lens barrel at least one of a maximum value and aminimum value of an image plane movement coefficient that representscorrespondence relationship between a movement amount of a focusadjustment lens included in the optical system and a movement amount ofan image plane; and a control unit that uses at least one of the maximumvalue and the minimum value of the image plane movement coefficient todetermine a drive speed for the focus adjustment lens when the focusdetection unit detects the focus adjustment state.

The focus adjustment control apparatus is, in the above focus adjustmentcontrol apparatus, characterized in that when the movement amount in anoptical axis direction of the focus adjustment lens is T_(L) and themovement amount of the image plane is T_(I), the image plane movementcoefficient is a coefficient that corresponds to a ratio defined byT_(L) and T_(I) and is determined depending on a lens position of thefocus adjustment lens.

The focus adjustment control apparatus is, in the above focus adjustmentcontrol apparatus, further characterized in that when the image planemovement coefficient is a coefficient that corresponds to T_(I)/T_(L),the control unit uses the maximum value of the image plane movementcoefficient to determine the drive speed which is a speed that allowsthe focus detection unit to detect the focus adjustment state even ifthe focus adjustment lens moves to a position at which the image planemovement coefficient is the maximum value of the image plane movementcoefficient, or when the image plane movement coefficient is acoefficient that corresponds to T_(L)/T_(I), the control unit uses theminimum value of the image plane movement coefficient to determine thedrive speed which is a speed that allows the focus detection unit todetect the focus adjustment state even if the focus adjustment lensmoves to a position at which the image plane movement coefficient is theminimum value of the image plane movement coefficient.

A focus adjustment control apparatus in another embodiment ischaracterized by comprising: a focus detection unit that calculates anevaluation value with regard to contrast of an image via an opticalsystem to detect a focus adjustment state of the optical system; anacquisition unit that acquires from a lens barrel an image planemovement coefficient that represents correspondence relationship betweena movement amount of a focus adjustment lens included in the opticalsystem and a movement amount of an image plane, and informationregarding a play amount of the optical system; a control unit thatperforms scan control for scanning by the focus adjustment lens when thefocus detection unit detects the focus adjustment state and performs,after the focus detection unit detects a focused position, focusingdrive control for moving the focus adjustment lens to the focusedposition; and a control unit that uses the image plane movementcoefficient and the play amount to determine whether or not to performreducing play in the focusing drive control.

The focus adjustment control apparatus is, in the above focus adjustmentcontrol apparatus, further characterized in that the control unit usesthe image plane movement coefficient and the play amount to calculate animage plane movement amount corresponding to the play amount andcompares the calculated image plane movement amount corresponding to theplay amount with a focal depth of an image via the optical system todetermine whether or not to perform reducing play in the focusing drivecontrol.

The focus adjustment control apparatus is, in the above focus adjustmentcontrol apparatus, further characterized in that the control unit usesthe image plane movement coefficient and the play amount to determinewhether or not to perform reducing play in the focusing drive control,the image plane movement coefficient corresponding to a lens position ofthe focus adjustment lens when the focus adjustment lens is reverselydriven to the focused position after the focused position is detected.

The focus adjustment control apparatus is, in the above focus adjustmentcontrol apparatus, further characterized in that when the movementamount in an optical axis direction of the focus adjustment lens isT_(L) and the movement amount of the image plane is T_(I), the imageplane movement coefficient is a coefficient that corresponds to a ratiodefined by T_(L) and T_(I), and when the image plane movementcoefficient is a coefficient that corresponds to T_(I)/T_(L), thecontrol unit uses a maximum value of the image plane movementcoefficient and the play amount to determine whether or not to performreducing play in the focusing drive control, or when the image planemovement coefficient is a coefficient that corresponds to T_(L)/T_(I),the control unit uses a minimum value of the image plane movementcoefficient and the play amount to determine whether or not to performreducing play in the focusing drive control.

The focus adjustment control apparatus, in the above focus adjustmentcontrol apparatus, further characterized in that the control unit usesthe image plane movement coefficient and the play amount to determinewhether or not to perform reducing play in the focusing drive control,the image plane movement coefficient corresponding to a lens position ofthe focus adjustment lens in the vicinity of the focused position of thefocus adjustment lens.

An imaging apparatus comprises any of the focus adjustment controlapparatuses discussed above.

A lens barrel is characterized by comprising: an optical system thatincludes a focus adjustment lens; a drive unit that drives the focusadjustment lens in an optical axis direction; a transceiver unit thatperforms transmission and reception of a signal between the lens barreland a camera body; and a control unit that, when receiving apredetermined signal from a camera body via the transceiver unit,transmits to the camera body via the transceiver unit at least one of amaximum value and a minimum value of an image plane movement coefficientthat represents correspondence relationship between a movement amount ofthe focus adjustment lens and a movement amount of an image plane.

The above lens barrel in embodiments is characterized by furthercomprising a storage unit that stores at least one of the maximum valueand the minimum value of the image plane movement coefficient.

The above lens barrel characterized in that the image plane movementcoefficient corresponds to a ratio defined by the movement amount in theoptical axis direction of the focus adjustment lens and the movementamount of the image plane on the optical axis.

A lens barrel in another embodiment is characterized by comprising: anoptical system that includes a focus adjustment lens; a drive unit thatdrives the focus adjustment lens in an optical axis direction; atransceiver unit that performs transmission and reception of a signalbetween the lens barrel and a camera body; and a control unit thatcontrols the transceiver unit so that the transceiver unit transmits, toa camera body, first information determined depending on a lens positionof the focus adjustment lens, wherein the control unit, when receiving apredetermined signal from a camera body via the transceiver unit,transmits to the camera body via the transceiver unit at least one of amaximum value and a minimum value of the first information.

The above lens barrel is in embodiments characterized in that when amovement amount of the focus adjustment lens is T_(L) and a movementamount of an image plane is T_(I), the first information is acoefficient that corresponds to T_(L)/T_(I) or a coefficient thatcorresponds to T_(I)/T_(L).

The lens barrel in further embodiments is characterized by comprising:an optical system that includes a focus adjustment lens; a drive unitthat drives the focus adjustment lens in an optical axis direction; atransceiver unit that performs transmission and reception of a signalbetween the lens barrel and a camera body; and a control unit thatcontrols the transceiver unit so that the transceiver unit transmits toa camera body a first image plane movement coefficient determineddepending on a lens position of the focus adjustment lens, wherein thecontrol unit, when receiving a predetermined signal from a camera bodyvia the transceiver unit, transmits to the camera body via thetransceiver unit a second image plane movement coefficient that does notdepend on the lens position of the focus adjustment lens.

The above lens barrel is in embodiments characterized in that the secondimage plane movement coefficient is at least one of a maximum value anda minimum value of the first image plane movement coefficient.

The above lens barrel is in embodiments characterized by furthercomprising a zoom lens drive unit that drives a zoom lens in the opticalaxis direction, wherein when a focal distance of the zoom lens does notvary, the second image plane movement coefficient does not vary even ifthe lens position of the focus adjustment lens varies, but when thefocal distance of the zoom lens varies, the second image plane movementcoefficient varies.

A camera body is characterized by comprising: a focus detection unitthat calculates an evaluation value with regard to contrast of an imagevia an optical system to detect a focus adjustment state of the opticalsystem; a transceiver unit that performs transmission and reception of asignal between the camera body and a lens barrel; and a control unitthat uses the signal received via the transceiver unit to perform drivecontrol for a focus adjustment lens included in the optical system,wherein the control unit controls the transceiver unit so that thetransceiver unit transmits to a lens barrel a first request signal thatrequests a first image plane movement coefficient determined dependingon a lens position of the focus adjustment lens and a second requestsignal that requests a second image plane movement coefficientdetermined not depending on the lens position of the focus adjustmentlens, and receives the first image plane movement coefficient and thesecond image plane movement coefficient from the lens barrel.

The above camera body is in embodiments characterized in that the secondimage plane movement coefficient is at least one of a maximum value anda minimum value of the first image plane movement coefficient.

The above camera body is in embodiments characterized in that when amovement amount in an optical axis direction of the focus adjustmentlens is T_(L) and a movement amount of an image plane is T_(I), theimage plane movement coefficient is a coefficient that corresponds to aratio defined by T_(L) and T_(I), and the control unit performs apredetermined operation when the image plane movement coefficient is acoefficient that corresponds to T_(I)/T_(L) and the first image planemovement coefficient corresponding to a current lens position of thefocus adjustment lens is determined to be larger than the second imageplane movement coefficient or when the image plane movement coefficientis a coefficient that corresponds to T_(L)/T_(I) and the first imageplane movement coefficient corresponding to a current lens position ofthe focus adjustment lens is determined to be smaller than the secondimage plane movement coefficient.

The above camera body is in embodiments characterized in that thecontrol unit performs a predetermined operation when the first imageplane movement coefficient equal to the second image plane movementcoefficient is not detected as a result of acquiring the first imageplane movement coefficient corresponding to a current lens position ofthe focus adjustment lens while driving the focus adjustment lens fromone end to the other end in an optical axis direction.

The above camera body is in embodiments characterized in that thepredetermined operation is at least one of control that performs searchdrive of the focus adjustment lens at a second speed lower than a firstspeed that is a search drive speed before the determination, controlthat prohibits notification to a photographer that a focused state isobtained, and control that prohibits the focus detection unit fromdetecting the focus adjustment state.

A camera system is characterized by comprising any of theabove-discussed camera bodies.

According to the present invention, a focus adjustment state of anoptical system can be appropriately detected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a camera according to embodiments ofthe present invention;

FIG. 2 is a front elevational view showing an imaging plane of animaging device shown in FIG. 1;

FIG. 3 is a front elevational view which enlarges part III of FIG. 2 toschematically show an arrangement of focus detection pixels 222 a and222 b;

FIG. 4(A) is a front elevational view showing enlarged one of imagingpixels 221;

FIG. 4(B) is a front elevational view showing enlarged one of the focusdetection pixels 222 a;

FIG. 4(C) is a front elevational view showing enlarged one of the focusdetection pixels 222 b;

FIG. 4(D) is a cross-sectional view showing enlarged one of the imagingpixels 221;

FIG. 4(E) is a cross-sectional view showing enlarged one of the focusdetection pixels 222 a;

FIG. 4(F) is a cross-sectional view showing enlarged one of the focusdetection pixels 222 b;

FIG. 5 is a cross-sectional view along line V-V of FIG. 3;

FIG. 6 depicts a table showing a relationship between a lens position ofa zoom lens 32 (focal distance) and a lens position of a focus lens 33(imaging distance), and an image plane movement coefficient K;

FIG. 7 is a flowchart showing operation of a first embodiment;

FIG. 8 is a view for explaining a play amount G of a drive transmissionmechanism for the focus lens 33;

FIG. 9 is a set of diagrams which show a relationship between a focuslens position and a focus evaluation value and relationships between afocus lens position and time when a scan operation and focusing drivebased on a contrast detection system are performed according to a belowembodiment;

FIG. 10 is a flowchart showing operation according to the secondembodiment;

FIG. 11 is a flowchart showing operation according to a thirdembodiment;

FIG. 12 is a flowchart showing operation according to a fourthembodiment;

FIG. 13 is a block diagram showing a camera according to a fifthembodiment;

FIG. 14 is a flowchart showing operation according to the fifthembodiment;

FIG. 15 is a flowchart showing an abnormality determination processaccording to the fifth embodiment;

FIG. 16 is a diagram showing an example of one scene for explaining aspecific example of the abnormality determination process according tothe fifth embodiment;

FIG. 17 depicts a table showing a relationship between the lens positionof the zoom lens 32 (focal distance) and a maximum image plane movementcoefficient K_(max);

FIG. 18 is a flowchart showing operation according to a sixthembodiment; and

FIG. 19 is a flowchart showing an abnormality determination processaccording to the sixth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will hereinafter be described withreference to the drawings.

First Embodiment

FIG. 1 is a view of the principal configuration which shows a digitalcamera 1 according to the present embodiment. The digital camera 1according to the present embodiment (referred simply to as “camera 1”,hereinafter) is configured of a camera body 2 and a lens barrel 3, sothat a mount unit 401 of the camera body 2 and a mount unit 402 of thelens barrel 3 are coupled with each other in a detachable manner.

The lens barrel 3 is an interchangeable lens which can be detachablyattached to the camera body 2. As shown in FIG. 1, the lens barrel 3 isprovided therein with an imaging optical system which includes lenses31, 32, 33 and 34 and an aperture 35.

The lens 33 is a focus lens, which can be moved in the optical axis L1direction thereby to allow the focal distance of the imaging opticalsystem to be adjusted. The focus lens 33 is provided so as to be movablealong the optical axis L1 of the lens barrel 3, and the position of thefocus lens 33 may be adjusted by a focus lens drive motor 331 whilebeing detected by an encoder 332 for the focus lens.

The specific configuration of the movement mechanism for the focus lens33 along the optical axis L1 is not particularly limited. As oneexample, a rotating barrel is inserted in a rotatable manner inside afixed barrel fixed to the lens barrel 3. The inner circumferentialsurface of this rotating barrel is formed with a helicoid groove (spiralgroove). The end of a lens frame to which the focus lens 33 is fixed isengaged with the helicoid groove. The focus lens drive motor 331 is usedto rotate the rotating barrel, so that the focus lens 33 fixed to thelens frame moves straight along the optical axis L1.

As described above, by rotating the rotating barrel with respect to thelens barrel 3, the focus lens 33 fixed to the lens frame moves straightin the optical axis L1 direction. The focus lens drive motor 331 as adrive source for the above movement is provided in the lens barrel 3.The focus lens drive motor 331 and the rotating barrel are, for example,coupled via a transmission comprising a plurality of gears. If the driveshaft of the focus lens drive motor 331 is driven to rotate to eitherdirection, then this driving force will be transmitted to the rotatingbarrel by a predetermined gear ratio to drive it in either direction,thereby moving the focus lens 33 fixed to the lens frame straight in acertain direction along the optical axis L1. If on the other hand, thedrive shaft of the focus lens drive motor 331 is driven to rotate in theopposite direction, then the gears of the transmission also rotate inthe opposite directions, and the focus lens 33 will move straight in theopposite direction along the optical axis L1.

The position of the focus lens 33 is detected by the encoder 332 for thefocus lens. As already described, the position in the optical axis L1direction of the focus lens 33 is correlated with the rotational angleof the rotating barrel, and can thus be determined by detecting therelative rotational angle of the rotating barrel with respect to thelens barrel 3, for example.

As the encoder 332 for the focus lens in the present embodiment, it ispossible to use one which detects rotation of a rotary disk coupled withthe rotational drive of the rotating barrel by a photo sensor such as aphoto interrupter so as to output a pulse signal corresponding to therotational speed, or one which brings an encoder pattern on the surfaceof a flexible printed circuit board provided at either one of the fixedbarrel and the rotating barrel into contact with a brush contact whichis provided at the other and detects the change in the contact positioncorresponding to the amount of movement of the rotating barrel (eitherin the rotational direction or optical axis direction) by a detectioncircuit, etc.

The focus lens 33 can be moved by rotation of the above-describedrotating barrel from the end at the camera body side (referred also toas “near end”) to the end at the object side (referred also to as“infinite end”) in the optical axis L1 direction. The encoder 332 forthe focus lens detects the current position of the focus lens 33 andoutputs current position information. A lens control unit 36 performscontrol to transmit the current position information to a camera controlunit 21. The camera control unit 21 uses the current positioninformation to calculate a drive target position of the focus lens 33, adrive speed for the focus lens 33, or an image plane movement speed(referred hereinafter to as “drive information”). The camera controlunit 21 performs control to transmit the drive information to the lenscontrol unit 36. On the basis of the drive information, the lens controlunit 36 performs drive control for the focus lens drive motor 331.

On the other hand, the lens 32 is a zoom lens, which can be moved in theoptical axis L1 direction thereby to allow the imaging magnification ofthe imaging optical system to be adjusted. Like in the case of theabove-described focus lens 33, the position of the zoom lens 32 may beadjusted by a zoom lens drive motor 321 while being detected by anencoder 322 for the zoom lens. The position of the zoom lens 32 can beadjusted by operating a zoom button provided on an operating unit 28 orby operating a zoom ring (not shown) provided on the lens barrel 3. Themovement mechanism for the zoom lens 32 along the optical axis L1 may bethe same as the above-described mechanism for the focus lens 33. Theconfigurations of the encoder 322 for the zoom lens and the zoom lensdrive motor 321 may also be the same as those of the encoder 332 for thefocus lens and the focus lens drive motor 331.

The aperture 35 is configured such that the aperture size centered onthe optical axis L1 can be adjusted in order to restrict the amount oflight beams which pass through the above imaging optical system andreach an imaging device 22 and to adjust the amount of blurring. Thesize of the aperture 35 is adjusted by a suitable aperture size, whichwas calculated in the automatic exposure mode, being sent from thecamera control unit 21 through the lens control unit 36, for example.This adjustment may also be performed by an aperture size, which was setin the manual operation using the operating unit 28 provided at thecamera body 2, being input from the camera control unit 21 to the lenscontrol unit 36. The aperture size of the aperture 35 is detected by anaperture sensor not shown, and the lens control unit 36 recognizes thecurrent aperture size.

A lens memory 37 is provided to store an image plane movementcoefficient K. The image plane movement coefficient K as used herein isa value that represents the correspondence relationship between thedrive amount of the focus lens 33 and the movement amount of an imageplane, and may be a ratio defined by the drive amount of the focus lens33 and the movement amount of an image plane, for example. According tothe present embodiment, the image plane movement coefficient can beobtained using Expression (1) below, for example, in which case as theimage plane movement coefficient K increases, the movement amount of animage plane due to driving the focus lens 33 also increases.(Image plane movement coefficient K)=(Movement amount of imageplane)/(Drive amount of focus lens 33)  (1)

In the camera 1 according to the present embodiment, even if the driveamount of the focus lens 33 is the same, different lens position of thefocus lens 33 gives a different movement amount of an image plane. In asimilar way, even if the drive amount of the focus lens 33 is the same,different lens position of the zoom lens 32 gives a different movementamount of an image plane. That is, the image plane movement coefficientvaries depending on the lens position in the optical axis of the focuslens 33 and further on the lens position in the optical axis of the zoomlens 32, and the lens control unit 36 according to the presentembodiment therefore operates to store the image plane movementcoefficient K for each lens position of the focus lens 33 and for eachlens position of the zoom lens 32.

FIG. 6 depicts a table which is stored in the lens memory 37 and showsthe relationship between the lens position of the zoom lens 32 (focaldistance) and the lens position of the focus lens 33 (imaging distance),and the image plane movement coefficient K. The table depicted in FIG. 6is configured such that the drive span of the zoom lens 32 is dividedinto nine segments of “f1” to “f9” in this order from the near end tothe infinite end while the drive span of the focus lens 33 is alsodivided into nine segments of “D1” to “D9” in this order from the nearend to the infinite end, thereby to store the image plane movementcoefficient K corresponding to each lens position. For example, when thelens position of the zoom lens 32 (focal distance) is at “f1” and thelens position of the focus lens 33 (imaging distance) is at “D1”, theimage plane movement coefficient K is “K11”. In the above example, thetable depicted in FIG. 6 is configured such that the drive span of eachlens is divided into nine segments, but the number of division is notparticularly limited and may freely be set.

With reference to FIG. 6, a maximum image plane movement coefficientK_(max) and a minimum image plane movement coefficient K_(min) will thenbe described.

The maximum image plane movement coefficient K_(max) as used herein is avalue that corresponds to the maximum value of the image plane movementcoefficient K. It is preferred that the maximum image plane movementcoefficient K_(max) varies depending on the current lens position of thezoom lens 32. It is also preferred that, when the current lens positionof the zoom lens 32 does not vary, the maximum image plane movementcoefficient K_(max) is a constant value (fixed value) even if thecurrent lens position of the focus lens 33 varies. It is thus preferredthat the maximum image plane movement coefficient K_(max) is a fixedvalue (constant value) that is determined depending on the lens positionof the zoom lens 32 (focal distance) and that does not depend on thelens position of the focus lens 33 (imaging distance).

For example, in FIG. 6, each of “K11”, “K21”, “K31”, “K41”, “K52”,“K62”, “K72”, “K82” and “K91” in gray cells is the maximum image planemovement coefficient K_(max) that represents a maximum value among theimage plane movement coefficients K at each lens position of the zoomlens 32 (focal distances). More specifically, provided that the lensposition of the zoom lens 32 (focal distance) is at “f1”, “K11” as theimage plane movement coefficient K when the lens position of the focuslens 33 (imaging distance) is at “D1” among “D1” to “D9” is the maximumimage plane movement coefficient K_(max) that represents a maximumvalue. Therefore, “K11” as the image plane movement coefficient K whenthe lens position of the focus lens 33 (imaging distance) is at “D1”represents a maximum value among “K11” to “K19” which are the imageplane movement coefficients K when respective lens positions (imagingdistances) are at “D1” to “D9”. In a similar way, provided that the lensposition of the zoom lens 32 (focal distance) is at “f2”, “K21” as theimage plane movement coefficient K when the lens position of the focuslens 33 (imaging distance) is at “D1” also represents a maximum valueamong “K21” to “K29” which are the image plane movement coefficients Kwhen respective lens positions (imaging distances) are at “D1” to “D9”.That is, “K21” is the maximum image plane movement coefficient K_(max).The same applies to the case where the lens position of the zoom lens 32(focal distance) is at each of “f3” to “f9”, in which case each of“K31”, “K41”, “K52”, “K62”, “K72”, “K82” and “K91” in gray cells is themaximum image plane movement coefficient K_(max).

In a similar way, the minimum image plane movement coefficient K_(min)as used herein is a value that corresponds to the minimum value of theimage plane movement coefficient K. It is preferred that the minimumimage plane movement coefficient K_(min) varies depending on the currentlens position of the zoom lens 32. It is also preferred that, when thecurrent lens position of the zoom lens 32 does not vary, the minimumimage plane movement coefficient K_(min) is a constant value (fixedvalue) even if the current lens position of the focus lens 33 varies.For example, in FIG. 6, each of “K19”, “K29”, “K39”, “K49”, “K59”,“K69”, “K79”, “K89” and “K99” in hatched cells is the minimum imageplane movement coefficient K_(min) that represents a minimum value amongthe image plane movement coefficients K at each lens position of thezoom lens 32 (focal distances).

In such a manner, as shown in FIG. 6, the lens memory 37 stores: theimage plane movement coefficients K that correspond to respective lenspositions of the zoom lens 32 (focal distances) and respective lenspositions of the focus lens 33 (imaging distances); the maximum imageplane movement coefficient K_(max) that represents a maximum value amongthe image plane movement coefficients K for each lens position of thezoom lens 32 (focal distance); and the minimum image plane movementcoefficient K_(min) that represents a minimum value among the imageplane movement coefficients K for each lens position of the zoom lens 32(focal distance).

Electrical contacts 403 provided at the mount unit 401 of the camerabody 2 and electrical contacts 404 provided at the mount unit 402 of thelens barrel 3 are connected with one another thereby to electricallyconnect the lens control unit 36 with the camera control unit 21 via alens transceiver unit 38 and a camera transceiver unit 29.

According to the present embodiment, the camera control unit 21 and thelens control unit 36 perform stationary communication therebetween andalso perform non-stationary communication as will be described later. Inthe stationary communication, the camera control unit 21 transmitsrepeatedly at a predetermined interval (e.g. interval of tensmilliseconds to hundreds milliseconds) a first request signal thatrequests lens information to the lens control unit 36 via the cameratransceiver unit 29 and the lens transceiver unit 38. After beinginitiated, the stationary communication may preferably be continued atthe predetermined interval until the power is turned off.

In addition, the camera control unit 21 transmits commands, such as fordriving the zoom lens 32, driving the focus lens 33 and adjusting theaperture size of the aperture 35, to the lens control unit 36.

The lens control unit 36, in the stationary communication, receivescommands such as for adjusting the aperture size and performs control onthe basis of the received commands. The lens control unit 36, whenreceiving the first request signal in the stationary communication,transmits repeatedly the lens information to the camera control unit 21.Examples of the lens information as used herein include information withregard to the position of the zoom lens 32, the position of the focuslens 33 and the aperture size of the aperture 35, etc. and a currentposition image plane movement coefficient K_(cur). The current positionimage plane movement coefficient K_(cur) as used herein is an imageplane movement coefficient K that corresponds to the current position ofthe zoom lens (focal distance) and the current position of the focuslens (imaging distance).

According to the present embodiment, the lens control unit 36 refers tothe table which is stored in the lens memory 37 and represents therelationship between the lens positions (position of zoom lens andposition of focus lens) and the image plane movement coefficient K,thereby to obtain the current position image plane movement coefficientK_(cur) which corresponds to the current lens position of the zoom lens32 and the current lens position of the focus lens 33.

In the non-stationary communication which is different from the abovestationary communication, the camera control unit 21 transmits a secondrequest signal for requesting transmission of the maximum image planemovement coefficient K_(max) and the minimum image plane movementcoefficient K_(min). It is preferred that the above non-stationarycommunication is interruptible communication to the stationarycommunication. The lens control unit 36, when receiving the secondrequest signal in the non-stationary communication, transmits themaximum image plane movement coefficient K_(max) and the minimum imageplane movement coefficient K_(mm) to the camera control unit 21.

The maximum image plane movement coefficient K_(max) is transmitted whenthe second request signal is received in the non-stationarycommunication, and differs from the current position image planemovement coefficient K_(cur) which is transmitted when the first requestsignal is received in the stationary communication.

Referring to FIG. 6, provided that the lens position of the zoom lens 32(focus distance) is at “f1” and the lens position of the focus lens 33(imaging distance) is at “D4”, for example, the lens control unit 36transmits “K14” as the current position image plane movement coefficientK_(cur) to the camera control unit 21 when receiving the first requestsignal from the camera control unit 21 in the stationary communication,and transmits “K11” as the maximum image plane movement coefficientK_(max) and “K19” as the minimum image plane movement coefficientK_(min) to the camera control unit 21 when receiving the second requestsignal from the camera control unit 21 in the non-stationarycommunication.

On the other hand, in the camera body 2, the imaging device 22 whichreceives light beams L1 from the above imaging optical system isprovided at a predetermined focal plane of the imaging optical system.At the front of the same, a shutter 23 is provided. The imaging device22 is configured of a device, such as CCD and CMOS, which converts thereceived optical signal to an electrical signal to send it to the cameracontrol unit 21. Captured image information sent to the camera controlunit 21 is sequentially sent to a liquid crystal drive circuit 25 and isdisplayed on an electronic viewfinder (EVF) 26 of a viewing opticalsystem. When a release button (not shown) provided at the operating unit28 is fully pressed, the captured image information is recorded in therecording medium, that is, a camera memory 24. The camera memory 24 canbe any of a detachable card type memory or built-in type memory. Detailsof the structure of the imaging device 22 will be described later.

The viewing optical system is provided in the camera body 2, for viewingthe image captured by the imaging device 22. The viewing optical systemin the present embodiment comprises: the electronic viewfinder (EVF) 26comprising a liquid crystal display element; the liquid crystal drivecircuit 25 which drives the electronic viewfinder 26; and an ocular lens27. The liquid crystal drive circuit 25 reads captured image informationwhich was captured by the imaging device 22 and was sent to the cameracontrol unit 21, and uses this as the basis to drive the electronicviewfinder 26. This allows the photographer to view the currentlycaptured image through the ocular lens 27. Instead of the above viewingoptical system using the optical axis L2 or in addition to this, it isalso possible to provide a liquid crystal display at the back surface ofthe camera body 2, etc. and display the captured image on this liquidcrystal display.

The camera control unit 21 is provided in the camera body 2. The cameracontrol unit 21, which is electrically connected with the lens controlunit 36 via the lens transceiver unit 38 and the camera transceiver unit29, transmits the first request signal in the stationary communicationto the lens control unit 36 at an interval of tens milliseconds tohundreds milliseconds as described above, and receives the lensinformation such as the current position image plane movementcoefficient K_(cur). In addition, the camera control unit 21 transmitscommands for performing adjustment of the aperture value, etc. to thelens control unit 36.

Further, the camera control unit 21, as described above, reads the pixeloutput from the imaging device 22, and processes the read pixel outputas necessary by a predetermined information process to generate imageinformation, which is output to the liquid crystal drive circuit 25 ofthe electronic viewfinder 26 and/or memory 24. In addition, the cameracontrol unit 21 controls the camera 1 as a whole, such as correction ofthe image information from the imaging device 22 and detection of thestate of focus adjustment of the lens barrel 3 and state of apertureadjustment, etc.

Further, the camera control unit 21, in addition to the above, uses thepixel data read from the imaging device 22 as the basis for detection ofa focus adjustment state of the imaging optical system by a phasedifference detection system and detection of a focus adjustment state ofthe imaging optical system by a contrast detection system. The specificmethod of detection of the focus adjustment state will be describedlater.

The operating unit 28 includes the shutter release button and inputswitches, such as a motion picture imaging start switch, for thephotographer to set various operating modes of the camera 1, and isdesigned to enable switching of the auto focus mode/manual focus modeand switching of the still picture imaging mode/motion picture imagingmode. The various modes set via the operating unit 28 are sent to thecamera control unit 21, which controls the operation of the camera 1 asa whole. The shutter release button includes a first switch SW1 which isturned on by half pressing of the button and a second switch SW2 whichis turned on by full pressing of the button.

The imaging device 22 according to the present embodiment will now beexplained.

FIG. 2 is a front elevational view which shows an imaging plane of theimaging device 22, and FIG. 3 is a front elevational view which enlargesarea III of FIG. 2 to schematically show the arrangement of focusdetection pixels 222 a and 222 b.

The imaging device 22 of the present embodiment, as shown in FIG. 3, isconfigured such that a plurality of imaging pixels 221 are arrangedtwo-dimensionally on the plane of the imaging plane, i.e., green pixelsG having color filters which pass the wavelength region of the greencolor, red pixels R having color filters which pass the wavelengthregion of the red color, and blue pixels B having color filters whichpass the wavelength region of the blue color, are arranged on aso-called “Bayer arrangement”. That is, in each group 223 of fouradjoining pixels (closely packed square lattice array), two green pixelsare arranged on one diagonal, while one red pixel and one blue pixel arearranged on the other diagonal. By using such groups 223 of pixelsarranged in a Bayer arrangement as units and arranging such groups 223of pixels on the imaging plane of the imaging device 22 repeatedlytwo-dimensionally, the imaging device 22 is configured.

The array in the unit pixel group 223 may also be a closely packedhexagonal lattice array instead of the illustrated closely packed squarelattice, for example. The configuration and array of the color filtersare not limited to the above. It is also possible to employ an array ofcomplementary color filters (green: G, yellow: Ye, magenta: Mg, andcyan: Cy).

FIG. 4(A) is a front elevational view which shows one of the imagingpixels 221 enlarged, while FIG. 4(D) is a cross-sectional view of thesame. One imaging pixel 221 is configured of a microlens 2211, aphotoelectric conversion unit 2212, and a not shown color filter. Asshown in the cross-sectional view of FIG. 4(D), the photoelectricconversion unit 2212 is built into the surface of a semiconductorcircuit board 2213 of the imaging device 22, while the microlens 2211 isformed on the surface of that. The photoelectric conversion unit 2212 isshaped to use the microlens 2211 to receive the imaging light beamspassing through an exit pupil (for example, F1.0) of the imaging opticalsystem, and thereby receives the imaging light beams.

In addition, at the center of the imaging plane of the imaging device 22and at the left and right symmetric positions from the center, that is,at three locations, focus detection pixel strings 22 a, 22 b and 22 care provided, at each of which focus detection pixels 222 a and 222 bare arranged as substitute for the above-described imaging pixels 221.As shown in FIG. 3, one focus detection pixel string is configured suchthat a plurality of focus detection pixels 222 a and 222 b are arrangedadjoining each other alternately in a horizontal string (22 a, 22 b, 22c). In the present embodiment, the focus detection pixels 222 a and 222b are densely arranged without gap at the positions of the green pixelsG and blue pixels B of the imaging pixels 221 arranged in a Bayerarrangement.

The positions of the focus detection pixel strings 22 a to 22 c shown inFIG. 2 are not limited to the illustrated positions. Strings may bearranged at any single location or two locations, or four or morelocations. Further, during actual focus detection, the photographer canalso manually operate the operating unit 28 to select a desired focusdetection pixel string as the focus detection area from among theplurality of arranged focus detection pixel strings 22 a to 22 c.

FIG. 4(B) is a front elevational view which shows one of the focusdetection pixels 222 a enlarged, while FIG. 4(E) is a cross-sectionalview of the focus detection pixel 222 a. FIG. 4(C) is a frontelevational view which shows one of the focus detection pixels 222 benlarged, while FIG. 4(F) is a cross-sectional view of the focusdetection pixel 222 b. The focus detection pixel 222 a, as shown in FIG.4(B), is configured of a microlens 2221 a and a semicircular shapedphotoelectric conversion unit 2222 a. As shown in the cross-sectionalview of FIG. 4(E), the photoelectric conversion unit 2222 a is builtinto the surface of a semiconductor circuit board 2213 of the imagingdevice 22, while the microlens 2221 a is formed on the surface of that.The focus detection pixel 222 b, as shown in FIG. 4(C), is configured ofa microlens 2221 b and a photoelectric conversion unit 2222 b. As shownin the cross-sectional view of FIG. 4(F), the photoelectric conversionunit 2222 b is built into the surface of a semiconductor circuit board2213 of the imaging device 22, while the microlens 2221 b is formed onthe surface of that. These focus detection pixels 222 a and 222 b, asshown in FIG. 3, are arranged mutually adjoining each other in ahorizontal string to thereby form the focus detection pixel strings 22 ato 22 c shown in FIG. 2.

The photoelectric conversion units 2222 a and 2222 b of the focusdetection pixels 222 a and 222 b are shaped to use the microlenses 2221a and 2221 b to receive the light beams passing through a predeterminedregion (for example, F2.8) of the exit pupil of the imaging opticalsystem. The focus detection pixels 222 a and 222 b are not provided withcolor filters, so that their spectral characteristics are combinationsof the spectral characteristics of the photodiodes which perform thephotoelectric conversion and the spectral characteristics of infraredcut filters not shown. Note, however, that each pixel may also beconfigured to comprise one of the same color filters as those of theimaging pixels 221, for example, the green filter.

The photoelectric conversion units 2222 a and 2222 b of the focusdetection pixels 222 a and 222 b shown in FIG. 4(B) and FIG. 4(C) aremade semicircular shapes, but the shapes of the photoelectric conversionunits 2222 a and 2222 b are not limited to this. Other shapes, forexample, oval shapes, rectangular shapes and polygonal shapes can alsobe used.

The description will now be directed to the so-called “phase differencedetection system” which detects the focus adjustment state of theimaging optical system on the basis of the pixel outputs of theabove-described focus detection pixels 222 a and 222 b.

FIG. 5 is a cross-sectional view along line V-V of FIG. 3, and showsthat the focus detection pixels 222 a-1, 222 b-1, 222 a-2 and 222 b-2arranged near the imaging optical axis L1 and adjoining one anotherreceive the light beams AB1-1, AB2-1, AB1-2 and AB2-2, respectively,which are emitted from the distance measuring pupils 351 and 352 of theexit pupil 350. In FIG. 5, among the plurality of focus detection pixels222 a and 222 b, only those positioned near the imaging optical axis Lare shown as examples, but the other focus detection pixels other thanthose shown in FIG. 5 are similarly configured to receive respectivelight beams emitted from the pair of distance measuring pupils 351 and352.

The “exit pupil 350” as used herein is an image which is set at theposition of the distance D in front of the microlenses 2221 a and 2221 bof the focus detection pixels 222 a and 222 b arranged at thepredetermined focus plane of the imaging optical system. The distance Dis the value unambiguously determined in accordance with the curvatureand the refractive index of the microlens and the distance between themicrolens and the photoelectric conversion unit, etc. This distance D isreferred to as the “distance measuring pupil distance”. The “distancemeasuring pupils 351 and 352” as used herein are images of thephotoelectric conversion units 2222 a and 2222 b which are projectedrespectively by the microlenses 2221 a and 2221 b of the focus detectionpixels 222 a and 222 b.

In FIG. 5, the direction of arrangement of the focus detection pixels222 a-1, 222 b-1, 222 a-2 and 222 b-2 matches the direction ofarrangement of the pair of distance measuring pupils 351 and 352.

As shown in FIG. 5, the microlenses 2221 a-1, 2221 b-1, 2221 a-2 and2221 b-2 of the focus detection pixels 222 a-1, 222 b-1, 222 a-2 and 222b-2 are arranged near the predetermined focal plane of the imagingoptical system. When the shapes of the photoelectric conversion units2222 a-1, 2222 b-1, 2222 a-2 and 2222 b-2 arranged behind themicrolenses 2221 a-1, 2221 b-1, 2221 a-2 and 2221 b-2 are projected onthe exit pupil 350 which is separated from the microlenses 2221 a-1,2221 b-1, 2221 a-2 and 2221 b-2 by exactly the distance measurementdistance D, the projected shapes form the distance measuring pupils 351and 352.

In other words, the relative positional relationships of the microlensesand the photoelectric conversion units in the focus detection pixels areset so that the projected shapes (distance measuring pupils 351 and 352)of the photoelectric conversion units of the focus detection pixelsmatch on the exit pupil 350 at the distance measurement distance D, andthe directions of projection of the photoelectric conversion units inthe focus detection pixels are thus determined.

As shown in FIG. 5, the photoelectric conversion unit 2222 a-1 of thefocus detection pixel 222 a-1 outputs a signal corresponding to theintensity of an image formed on the microlens 2221 a-1 by the light beamAB1-1 which passes through the distance measuring pupil 351 and headstoward the microlens 2221 a-1. Similarly, the photoelectric conversionunit 2222 a-2 of the focus detection pixel 222 a-2 outputs a signalcorresponding to the intensity of an image formed on the microlens 2221a-2 by the light beam AB1-2 which passes through the distance measuringpupil 351 and heads toward the microlens 2221 a-2.

The photoelectric conversion unit 2222 b-1 of the focus detection pixel222 b-1 outputs a signal corresponding to the intensity of an imageformed on the microlens 2221 b-1 by the light beam AB2-1 which passesthrough the distance measuring pupil 352 and heads toward the microlens2221 b-1. Similarly, the photoelectric conversion unit 2222 b-2 of thefocus detection pixel 222 b-2 outputs a signal corresponding to theintensity of an image formed on the microlens 2221 b-2 by the light beamAB2-2 which passes through the distance measuring pupil 352 and headstoward the microlens 2221 b-2.

By arranging the above-described two types of plural focus detectionpixels 222 a and 222 b in a straight line as shown in FIG. 3 andgrouping the outputs of the photoelectric conversion units 2222 a and2222 b of the focus detection pixels 222 a and 222 b into respectiveoutput groups corresponding to the distance measuring pupils 351 and352, data is obtained relating to the intensity distributions of thepair of images which the focus detection beams passing through thedistance measuring pupils 351 and 352 form on the focus detection pixelstrings. This intensity distribution data can be processed by imagedeviation detection operation, such as correlation operation or phasedifference detection, thereby to detect an image deviation amount by theso-called phase difference detection system.

Further, by processing the obtained image deviation amount usingconversion operation depending on the interval between the centers ofgravity of the pair of distance measuring pupils, it is possible to findthe deviation of the current focal plane with respect to thepredetermined focal plane (focal plane at focus detection areacorresponding to position of microlens array on predetermined focalplane), that is, the defocus amount.

The calculation of the image deviation amount using the phase differencedetection system and the calculation of the defocus amount based thereonare performed by the camera control unit 21.

Further, the camera control unit 21 reads out the outputs of the imagingpixels 221 of the imaging device 22 and uses the read out pixel outputsas the basis to calculate a focus evaluation value. This focusevaluation value can be obtained, for example, by extracting the highfrequency components of the image outputs from the imaging pixels 221 ofthe imaging device 22 using a high frequency pass filter. In analternative embodiment, it may be obtained by using two high frequencypass filters with different cutoff frequencies to extract the highfrequency components.

The camera control unit 21 then sends a drive signal to the lens controlunit 36 to drive the focus lens 33 at a predetermined sampling interval(distance), thereby obtaining focus evaluation values at differentpositions and finding the position of the focus lens 33 at which thefocus evaluation value is maximum as a focused position, i.e.,performing focus detection by the contrast detection system. Thisfocused position can be obtained, for example, when calculating thefocus evaluation values while driving the focus lens 33, byinterpolation or other appropriate operation using those focusevaluation values which take a value that rises twice and thereafterdrops twice.

An example of the operation of the camera 1 according to the presentembodiment will then be described with reference to FIG. 7. FIG. 7 is aflowchart showing an example of the operation of the camera 1 accordingto the present embodiment. The following operation is initiated by thepower of the camera 1 being turned on.

First at step S101, the camera control unit 21 initiates calculation ofthe defocus amount using the phase difference detection system.According to the present embodiment, the calculation process for thedefocus amount using the phase difference detection system is performedas follows. That is, the camera control unit 21 first reads out a pairof image data corresponding to a pair of images from the focus detectionpixels 222 a and 222 b which constitute each of the three focusdetection pixel strings 22 a to 22 c of the imaging device 22. In thiscase, a configuration is also possible such that when manual operationby the photographer selects a specific focus detection position, onlythe data from the focus detection pixels corresponding to that focusdetection position is read out. The camera control unit 21 then uses theread-out pair of image data as the basis to perform image deviationdetection processing (correlation processing), and calculates an imagedeviation amount at the focus detection position corresponding to eachof the three focus detection pixel strings 22 a to 22 c, which isfurther converted to the defocus amount. In addition, the camera controlunit 21 performs evaluation of the reliability of the calculated defocusamount. Evaluation of the reliability of the defocus amount may forexample be performed on the basis of the degree of match of the pair ofimage data and/or contrast, etc. Such calculation processing of thedefocus amount using the phase difference detection system is performedrepeatedly at a predetermined interval.

At step S102, the camera control unit 21 initiates a calculation processfor the focus evaluation value using the contrast detection system.According to the present embodiment, the calculation process for thefocus evaluation value is performed by reading out pixel outputs fromthe imaging pixels 221 of the imaging device 22, extracting highfrequency components of the read-out pixel outputs using a highfrequency pass filter, and accumulating them. If a specific focusdetection position is selected by manual operation by the photographer,another configuration may also be possible such that pixel outputs areread out only from the imaging pixels 221 corresponding to the selectedfocus detection position to calculate the focus evaluation value. Thecalculation process for the focus evaluation value is performedrepeatedly at a predetermined interval.

According to the present embodiment, at step S101, at a timing when thephase difference detection system initiates calculation of the defocusamount or at a timing when the contrast detection system initiates acalculation process for the focus evaluation value, or after they areinitiated, the stationary communication is initiated between the cameracontrol unit 21 and the lens control unit 36, and a process is performedrepeatedly at a predetermined interval such that the lens control unit36 transmits to the camera control unit 21 lens information whichincludes the current position image plane movement coefficient K_(cur)corresponding to the current lens position of the zoom lens 32 and thecurrent lens position of the focus lens 33.

At step S103, the camera control unit 21 makes a determination whetheror not the shutter release button provided at the operating unit 28 washalf pressed (first switch SW1 turned on). If the first switch SW1 wasturned on, then the routine proceeds to step S104, while on the otherhand, if the first switch SW1 is not turned on, then the routine standsby at step S103 at which calculation of the defocus amount andcalculation of the focus evaluation value and further acquisition oflens information using the stationary communication are performedrepeatedly until the first switch SW1 is turned on.

At step S104, the camera control unit 21 transmits the second requestsignal in the non-stationary communication, and the lens control unit36, after receiving the second request signal in the non-stationarycommunication from the camera control unit 21, refers to the table (seeFIG. 6) stored in the lens memory 37 to transmit to the camera controlunit 21 the maximum image plane movement coefficient K_(max) and theminimum image plane movement coefficient K_(min) that correspond to thecurrent lens position of the zoom lens 32. The camera control unit 21thus receives the maximum image plane movement coefficient K_(max) andthe minimum image plane movement coefficient K_(min).

At step S105, the camera control unit 21 makes a determination whetheror not the defocus amount was able to be calculated using the phasedifference detection system. If the defocus amount was able to becalculated, then the routine proceeds to step S111, while on the otherhand, if the defocus amount was not able to be calculated, then theroutine proceeds to step S106. Note that, according to the presentembodiment, even though the defocus amount was able to be calculated,cases where the calculated defocus amount has low reliability aretreated as if the defocus amount was not able to be calculated, and theroutine is to proceed to step S106. According to the present embodiment,the reliability of the defocus amount may be determined to be low if thecontrast of the object is low, the object is a very low brightnessobject, or the object is a very high brightness object, for example.

The above determination at step S105 is made using a result of the mostrecent one-time defocus amount calculation process, but an alternativeembodiment may be configured such that, if the defocus amount wassuccessively not able to be calculated or the reliability of the defocusamount was successively low in the most recent predetermined number ofdefocus amount calculation processes, then the measurement of distanceis determined not to be possible and the routine proceeds to step S106,while in contrast, if at least one defocus amount was able to becalculated in the most recent predetermined number of defocus amountcalculation processes, then the measurement of distance is determined tobe possible and the routine proceeds to step S111.

If, at step S105, the defocus amount was determined to be able to becalculated so that the measurement of distance was determined possible,then the routine proceeds to step S111 at which focusing drive isperformed on the basis of the defocus amount calculated using the phasedifference detection system. Specifically, the camera control unit 21calculates, from the defocus amount calculated using the phasedifference detection system, a lens drive amount that is necessary todrive the focus lens 33 to the focused position, which is sent to thefocus lens drive motor 331 via the lens control unit 36. This allows thefocus lens drive motor 331 to drive the focus lens 33 to the focusedposition on the basis of the lens drive amount calculated by the cameracontrol unit 21.

Note that, according to the present embodiment, even while the focuslens drive motor 331 is driven to drive the focus lens 33 to the focusedposition, the camera control unit 21 performs repeatedly calculation ofthe defocus amount using the phase difference detection system, so thatif a new defocus amount is calculated, then the camera control unit 21drives the focus lens 33 on the basis of the new defocus amount.

Then at step S106, the camera control unit 21 uses the maximum imageplane movement coefficient K_(max) acquired at step S104 to perform aprocess of determining a scan drive speed V that is a drive speed forthe focus lens 33 in a scan operation. The “scan operation” as usedherein is an operation in which the camera control unit 21 concurrentlyperforms calculation of the defocus amount using the phase differencedetection system and calculation of the focus evaluation value using thecontrast detection system at a predetermined interval while driving thefocus lens 33 using the focus lens drive motor 331 at the scan drivespeed V determined at step S106, thereby to concurrently and parallellyperform detection of a focused position using the phase differencedetection system and detection of a focused position using the contrastdetection system at a predetermined interval.

In this scan operation, when the focused position detecting is performedusing the contrast detection system, the camera control unit 21calculates focus evaluation values at a predetermined sampling intervalwhile driving the focus lens 33 for scan, and detects a lens position atwhich the calculated focus evaluation value is a peak, as the focusedposition. Specifically, the camera control unit 21 drives the focus lens33 for scan to move an image plane of the optical system in the opticalaxis direction thereby, calculates focus evaluation values at differentimage planes, and detects a lens position at which the focus evaluationvalue is a peak, as the focused position. If, however, the movementspeed of the image plane is unduly high, then the interval of imageplanes for calculating the focus evaluation values becomes excessivelylarge, so that the focused position may not appropriately be detected.In particular, the image plane movement coefficient K representing themovement amount of an image plane to the drive amount of the focus lens33 varies depending on the lens position in the optical axis of thefocus lens 33, and hence, even when the focus lens 33 is driven at aconstant speed, some lens positions of the focus lens 33 cause themovement speed of an image plane to be unduly high, and the interval ofimage planes for calculating the focus evaluation values thus becomesexcessively large, so that the focused position may not appropriately bedetected.

Therefore, according to the present embodiment, the camera control unit21 uses the maximum image plane movement coefficient K_(max) acquired atstep S106 as the basis to calculate the scan drive speed V at the timeof driving the focus lens 33 for scan. The camera control unit 21 usesthe maximum image plane movement coefficient K_(max) to calculate thescan drive speed V so that it is a maximum drive speed among thosecapable of being used to appropriately detect the focused position usingthe contrast detection system.

Then at step S107, the scan operation is initiated using the scan drivespeed V determined at step S106. Specifically, the camera control unit21 sends a scan drive initiation command to the lens control unit 36,which uses the command as the basis to drive the focus lens drive motor331 so that the focus lens 33 is driven for scan at the scan drive speedV determined at step S106. The camera control unit 21 then operates to:read out a pair of image data corresponding to a pair of images from thefocus detection pixels 222 a and 222 b of the imaging device 22 at apredetermined interval while driving the focus lens 33 at the scan drivespeed V; use the read-out data as the basis to perform calculation ofthe defocus amount using the phase difference detection system andevaluation of the reliability of the calculated defocus amount; read outpixel outputs from the imaging pixels 221 of the imaging device 22 at apredetermined interval while driving the focus lens 33 at the scan drivespeed V; and use the read-out pixel outputs as the bases to calculateand acquire focus evaluation values at different focus lens positionsthereby to perform detection of the focused position using the contrastdetection system.

Then at step S108, the camera control unit 21 makes a determinationwhether or not the defocus amount was able to be calculated using thephase difference detection system as a result of the scan operation. Ifthe defocus amount was able to be calculated, then the measurement ofdistance is determined to be possible and the routine proceeds to stepS111, while on the other hand, if the defocus amount was not able to becalculated, then the measurement of distance is determined not to bepossible and the routine proceeds to step S109. Note that, also at stepS108, like at step S105, even though the defocus amount was able to becalculated, cases where the calculated defocus amount has lowreliability are treated as if the defocus amount was not able to becalculated, and the routine is to proceed to step S109.

At step S109, the camera control unit 21 makes a determination whetheror not the focused position was able to be detected using the contrastdetection system as a result of the scan operation. If the focusedposition was able to be detected using the contrast detection system,then the routine proceeds to step S112, while on the other hand, if thefocused position was not able to be detected, then the routine proceedsto step S110.

At step S110, the camera control unit 21 makes a determination whetheror not the scan operation has been performed for the whole of thedrivable range of the focus lens 33. If the scan operation is notperformed for the whole of the drivable range of the focus lens 33, thenthe routine returns to step S108, and steps S108 to S110 are repeatedthereby continuing to perform the scan operation, that is, an operationto concurrently perform calculation of the defocus amount using thephase difference detection system and detection of the focused positionusing the contrast detection system at a predetermined interval whiledriving the focus lens 33 for scan. If, on the other hand, the scanoperation is completed for the whole of the drivable range of the focuslens 33, then the routine proceeds to step S113.

As a result of the scan operation executed, if the determination wasmade at step S108 that the defocus amount was able to be calculatedusing the phase difference detection system, then, after processing tostop the scan operation, the routine proceeds to step S111 at which thefocusing drive is performed as described above to drive the focus lens33 to the focused position detected using the phase difference detectionsystem.

Further, as a result of the scan operation executed, if thedetermination was made at step S109 that the focused position was ableto be detected using the contrast detection system, then, afterprocessing to stop the scan operation, the routine proceeds to step S112at which the camera control unit 21 performs the focusing drive to drivethe focus lens 33 to the focused position detected using the contrastdetection system.

If the drive of the focus lens 33 was completed after driving the focuslens 33 to the focused position detected using the phase differencedetection system or to the focused position detected using the contrastdetection system, then the focusing completed is displayed via theelectronic viewfinder 26.

If on the other hand, the determination was made at step S110 that theexecution of the scan operation was completed for the whole of thedrivable range of the focus lens 33, then the routine proceeds to stepS113. At step S113, processing is performed to end the scan operationbecause as a result of the scan operation performed, the focusedposition was not able to be detected using the contrast detectionsystem, and thereafter the focusing being impossible is displayed. Thedisplay of the focusing being impossible is performed using theelectronic viewfinder 26, for example.

As described above, according to the present embodiment, the maximumimage plane movement coefficient K_(max), which represents a maximumimage plane movement coefficient among a plurality of image planemovement coefficients K stored for respective positions of the focuslens 33, is acquired from the lens control unit 36. The camera controlunit 21 uses the maximum image plane movement coefficient K_(max) tocalculate the scan drive speed V so that it is a maximum drive speedamong those capable of being used to appropriately detect the focusedposition using the contrast detection system, and hence, the calculationinterval for the focus evaluation values (interval of image planes forcalculating focus evaluation values) has a value suitable for focusdetection even if the focus lens 33 is driven for scan to a position atwhich the image plane movement coefficient K is a maximum value (e.g. avalue equal to the maximum image plane movement coefficient K_(max)).

This allows the focused position to appropriately be detected using thecontrast detection system according to the present embodiment even ifthe image plane movement coefficient K becomes large (e.g. a case ofbeing the maximum image plane movement coefficient K_(max)) as a resultof the image plane movement coefficient K varying as the focus lens 33is driven in the optical axis direction.

The above-described embodiment exemplifies a configuration in which themaximum image plane movement coefficient K_(max), which represents amaximum image plane movement coefficient among a plurality of imageplane movement coefficients K stored for respective positions of thefocus lens 33, is acquired from the lens barrel 3, and the scanoperation is performed using a scan speed V which is the maximum drivespeed for the focus lens 33 that allows the focus detection toappropriately be performed using the contrast detection system even ifthe image plane movement coefficient K at the time of driving the focuslens 33 is the same as the acquired maximum image plane movementcoefficient K_(max), but the present invention is not limited to thisconfiguration, and another configuration may also be employed as below,for example.

That is, a larger one of two coefficients is acquired as a predeterminedimage plane movement coefficient K_(pre) from the lens barrel 3, whereinone of the two coefficients is a first image plane movement coefficientK₁ that corresponds to a first position at the near end side from thecurrent lens position of the focus lens 33 while the other is a secondimage plane movement coefficient K₂ that corresponds to a secondposition at the infinite end side from the current lens position of thefocus lens 33. In this case, a configuration may be employed such thatthe scan operation is performed using a scan speed V which is themaximum drive speed for the focus lens 33 that allows the focusdetection to appropriately be performed using the contrast detectionsystem even if the image plane movement coefficient K at the time ofdriving the focus lens 33 is the predetermined image plane movementcoefficient K_(pre) when the scan operation is performed.

Or, if a predetermined image plane movement coefficient K_(pre) thatcorresponds to a predetermined lens position of the focus lens 33 islarger than the image plane movement coefficient K_(cur) at the currentlens position of the focus lens 33, then the predetermined image planemovement coefficient K_(pre) is to be acquired from the lens barrel 3.In this case, a configuration may be employed such that the scanoperation is performed using a scan speed V which is the maximum drivespeed for the focus lens 33 that allows the focus detection toappropriately be performed using the contrast detection system even ifthe image plane movement coefficient K at the time of driving the focuslens 33 is the acquired predetermined image plane movement coefficientK_(pre) when the scan operation is performed.

An alternative configuration may be employed such that the operationaccording to the above-described embodiment is executed only when a highmagnification zoom lens is used as the lens barrel 3. A highmagnification zoom lens has a tendency that the image plane movementcoefficient becomes large, and the accuracy in detection of the focusedposition using the contrast detection system can thus be enhancedcompared with the conventional technique.

Second Embodiment

A second embodiment according to the present invention will then bedescribed. The second embodiment has the same configuration as that ofthe above-described first embodiment except that the camera 1 shown inFIG. 1 operates as will be described below.

That is, the second embodiment has an additional feature that, in theflowchart shown in FIG. 7, after the focused position was able to bedetected at step S109 using the contrast detection system, whenperforming at step S112 the focusing drive on the basis of the result ofthe contrast detection system, a determination is made whether or not toperform drive for reducing play, and this determination is used as thebasis to change the drive scheme for the focus lens 33 at the time ofperforming the focusing drive from the scheme in the above-describedfirst embodiment, so in this respect the second embodiment differs fromthe first embodiment, but other features are the same as those of thefirst embodiment.

In general, the focus lens drive motor 331 for driving the focus lens 33as shown in FIG. 1 is configured of a mechanical drive transmissionmechanism which, for example, comprises a first drive mechanism 500 anda second drive mechanism 600 as shown in FIG. 8, and is configured suchthat the first drive mechanism 500 is driven to drive the second drivemechanism 600 at the side of the focus lens 33 thereby to move the focuslens 33 to the near end side or the infinite end side. In such a drivetransmission mechanism, a play amount G is ordinarily provided in viewof smooth operation of engaging parts of gears. In the contrastdetection system, however, due to its mechanism, the focus lens 33 mayhave to be driven as shown in (A) and (B) of FIG. 9 such that the focuslens 33 once passes through the focused position in the scan operationand then moves to the focused position after reversing the drivingdirection. Thus, the characteristic in this case is such that, if thedrive for reducing play is not performed as shown in (B) of FIG. 9, thenthe lens position of the focus lens 33 is shifted exactly by the playamount G. For this reason, in order to eliminate such an effect due tothe play amount G, as shown in (A) of FIG. 9, when performing thefocusing drive for the focus lens 33, it may be necessary to perform thedrive for reducing play in which the focus lens 33 once passes throughthe focused position and is then driven to the focused position byreversing again the driving direction.

FIG. 9 is a set of diagrams which show a relationship between the focuslens position and the focus evaluation value and relationships betweenthe focus lens position and time when the scan operation and thefocusing drive based on the contrast detection system are performedaccording to the present embodiment. (A) of FIG. 9 shows an aspect that,after initiating at time t₀ the scan operation for the focus lens 33from the lens position P0 in the direction from the infinite end side tothe near end side, if the peak position (focused position) P2 of thefocus evaluation value is detected at the time when the focus lens 33 ismoved to the lens position P1 at time t₁, then the scan operation isstopped and the focusing drive is performed along with the drive forreducing play thereby to drive the focus lens 33 to the focused positionat time t₂. On the other hand, (B) of FIG. 9 shows an aspect that, afterinitiating at time t₀ the scan operation in the same way, the scanoperation is stopped at time t₁ and the focusing drive is performedwithout the drive for reducing play thereby to drive the focus lens 33to the focused position at time t₃.

An example of operation according to the second embodiment will now bedescribed with reference to the flowchart shown in FIG. 10. Theoperation below is executed if the focused position was detected usingthe contrast detection system at step S109 in the above-describedflowchart shown in FIG. 7. That is, as shown in (A) and (B) of FIG. 9,after initiating the scan operation from time t₀, if the peak position(focused position) P2 of the focus evaluation value was detected at thetime when the focus lens 33 was moved to the lens position P1 at timet₁, then the operation is executed from at time t₁.

More specifically, if the focused position is detected using thecontrast detection system, then the camera control unit 21 performs atstep S201 acquisition of the current position image plane movementcoefficient K_(cur) at the current position of the zoom lens 32 and thecurrent position of the focus lens 33. For example, referring to (A) and(B) of FIG. 9, a current image plane movement coefficient Kcorresponding to the lens position P1 at time t₀ is acquired as thecurrent position image plane movement coefficient K_(cur). The currentposition image plane movement coefficient K_(cur) can be acquired fromthe lens control unit 36 via the lens transceiver unit 38 and the cameracontrol unit 21 using the above-described stationary communication whichis being performed between the camera control unit 21 and the lenscontrol unit 36.

Then at step S202, the camera control unit 21 performs acquisition ofinformation regarding the play amount G (see FIG. 8) of the drivetransmission mechanism for the focus lens 33. The play amount G of thedrive transmission mechanism for the focus lens 33 can be acquired forexample by preliminarily storing it in the lens memory 37 provided inthe lens barrel 3 and referring to it. More specifically, the cameracontrol unit 21 sends a transmission request for the play amount G ofthe drive transmission mechanism for the focus lens 33 to the lenscontrol unit 36 via the camera transceiver unit 29 and the lenstransceiver unit 38 so that the lens control unit 36 transmits the playamount G of the drive transmission mechanism for the focus lens 33stored in the lens memory 37. An alternative embodiment may also bepossible such that the information regarding the play amount G of thedrive transmission mechanism for the focus lens 33 stored in the lensmemory 37 is incorporated in the lens information to be transmitted andreceived in the above-described stationary communication which is beingperformed between the camera control unit 21 and the lens control unit36.

Then at step S203, the camera control unit 21 calculates an image planemovement amount I_(G) corresponding to the play amount G on the basis ofthe above-described current position image plane movement coefficientK_(cur) acquired at step S201 and the above-described informationregarding the play amount G of the drive transmission mechanism for thefocus lens 33 acquired at step S202. The image plane movement amountI_(G) corresponding to the play amount G is a movement amount of theimage plane when the focus lens is driven exactly by the same amount asthe play amount G, and can be calculated in accordance with Expression(2) below in the present embodiment.(Image plane movement amount I _(G) corresponding to play amountG)=(Play amount G)×(Current position image plane movement coefficient K_(cur))  (2)

Then at step S204, the camera control unit 21 performs a process ofcomparing the above-described image plane movement amount I_(G)corresponding to the play amount G calculated at step S203 with apredetermined image plane movement amount I_(P), and the result of thiscomparison is used to make a determination whether the image planemovement amount I_(G) corresponding to the play amount G is not largerthan the predetermined image plane movement amount I_(P), i.e., whethera condition of (Image plane movement amount I_(G) corresponding to playamount G)≦(Predetermined image plane movement amount I_(P)) is satisfiedor not. The predetermined image plane movement amount I_(P) may be setto correspond to the focal depth of the optical system, and isordinarily to be an image plane movement amount that corresponds to thefocal depth. An alternative embodiment may also be possible such thatthe predetermined image plane movement amount I_(P) is appropriately setdepending on the F-value, cell size of the imaging device 22 or theformat of an image to be captured, etc. because the predetermined imageplane movement amount I_(P) is set to correspond to the focal depth ofthe optical system. Specifically, the predetermined image plane movementamount I_(P) may be set a larger value as the F-value increases.Alternatively or in addition, the predetermined image plane movementamount I_(P) may be set at a larger value as the cell size of theimaging device 22 increases or the image format is reduced. If the imageplane movement amount I_(G) corresponding to the play amount G is notlarger than the predetermined image plane movement amount I_(P), thenthe routine proceeds to step S205. If, on the other hand, the imageplane movement amount I_(G) corresponding to the play amount G is largerthan the predetermined image plane movement amount I_(P), then theroutine proceeds to step S206.

At step S205, it has been determined at the above-described step S204that the image plane movement amount I_(G) corresponding to the playamount G is not larger than the predetermined image plane movementamount I_(P), in which case it is determined that the lens position ofthe focus lens 33 after the drive can fall within the focal depth of theoptical system even without the drive for reducing play and that thedrive for reducing play is not to be performed at the time of focusingdrive, and such determination is used as the basis to perform thefocusing drive without the drive for reducing play. That is, adetermination is made that the focus lens 33 is driven directly to thefocused position at the time of performing the focusing drive, and thisdetermination is used as the basis to perform the focusing drive withoutthe drive for reducing play, as shown in (B) of FIG. 9.

At step S206, on the other hand, it has been determined at theabove-described step S204 that the image plane movement amount I_(G)corresponding to the play amount G is larger than the predeterminedimage plane movement amount I_(P), in which case it is determined thatthe lens position of the focus lens 33 after the drive cannot fallwithin the focal depth of the optical system if the drive for reducingplay is not performed and that the drive for reducing play is to beperformed at the time of focusing drive, and such determination is usedas the basis to perform the focusing drive along with the drive forreducing play. That is, a determination is made that, at the time ofperforming the focusing drive, the focus lens 33 is driven to once passthrough the focused position and then driven to the focused position byreversing again the driving direction, and this determination is used asthe basis to perform the focusing drive along with the drive forreducing play, as shown in (A) of FIG. 9.

According to the second embodiment, as described above, the currentposition image plane movement coefficient K_(cur) and the informationregarding the play amount G of the drive transmission mechanism for thefocus lens 33 are used as the basis to calculate the image planemovement amount I_(G) corresponding to the play amount G, and adetermination is made whether the calculated image plane movement amountI_(G) corresponding to the play amount G is not larger than thepredetermined image plane movement amount I_(P) corresponding to thefocal depth of the optical system, thereby to determine whether or notto perform the drive for reducing play at the time of performing thefocusing drive. As a result of the determination, if the image planemovement amount I_(G) corresponding to the play amount G is not largerthan the predetermined image plane movement amount I_(P) correspondingto the focal depth of the optical system and the lens position of thefocus lens 33 after the drive can therefore fall within the focal depthof the optical system, then the drive for reducing play is notperformed, while on the other hand, if the image plane movement amountI_(G) corresponding to the play amount G is larger than thepredetermined image plane movement amount I_(P) corresponding to thefocal depth of the optical system and the lens position of the focuslens 33 after the drive therefore cannot fall within the focal depth ofthe optical system without the drive for reducing play, then the drivefor reducing play is performed. Therefore, according to the presentembodiment, if the drive for reducing play is not necessary, then thedrive for reducing play is not performed, so that the time required forthe focusing drive can be reduced, and the time relevant to the focusingoperation can thereby be reduced. On the other hand, if the drive forreducing play is necessary, then the drive for reducing play isperformed and the accuracy in focusing can thus be enhanced.

In particular, according to the second embodiment, the image planemovement coefficient K, which varies depending on the lens position ofthe zoom lens 32 and the lens position of the focus lens 33, is used tocalculate the image plane movement amount I_(G) corresponding to theplay amount G, which is compared with the predetermined image planemovement amount I_(P) corresponding to the focal depth of the opticalsystem, and it can thereby be possible to appropriately determinewhether the drive for reducing play at the time of focusing is necessaryor not.

Third Embodiment

A third embodiment according to the present invention will then bedescribed. The third embodiment has the same configuration as that ofthe above-described second embodiment except that the camera 1 shown inFIG. 1 operates as will be described below.

The above-described second embodiment has been exemplified in which theimage plane movement amount I_(G) corresponding to the play amount G iscalculated using the current position image plane movement coefficientK_(cur) that corresponds to the lens position of the zoom lens 32 andthe lens position of the focus lens 33 at the time of initiating thereverse drive after completing the scan operation for the focus lens 33when calculating the image plane movement amount I_(G) corresponding tothe play amount G. In contrast, according to the third embodiment, themaximum image plane movement coefficient K_(max) corresponding to thecurrent lens position of the zoom lens 32 is used as substitute for thecurrent position image plane movement coefficient K_(cur) to calculatethe image plane movement amount I_(G) corresponding to the play amountG, and in this regard the third embodiment differs from theabove-described second embodiment.

An example of operation according to the third embodiment will now bedescribed with reference to the flowchart shown in FIG. 11. Like in theabove-described second embodiment, the operation below is executed ifthe focused position was detected using the contrast detection system atstep S109 in the above-described flowchart shown in FIG. 7.

More specifically, if the focused position is detected using thecontrast detection system, then the camera control unit 21 performs atstep S301 acquisition of the maximum image plane movement coefficientK_(max) at the current position of the zoom lens 32. For example, if thelens position of the zoom lens 32 (focal distance) is at “f5” in thetable shown in FIG. 6, then “K52” in gray cell is acquired as themaximum image plane movement coefficient K_(max).

According to the present embodiment, the timing when the camera controlunit 21 acquires the maximum image plane movement coefficient K_(max)may be a time when the reverse drive of the focus lens 33 is executedafter the focused position was detected using the contrast detectionsystem, but may otherwise be a time when the shutter release buttonprovided at the operating unit 28 was half pressed (first switch SW1turned on) or a time when the focus adjustment operation was initiateddue to the half-press of the shutter release button. That is, for theacquisition of the maximum image plane movement coefficient K_(max) atthe time when the shutter release button was half pressed or at the timewhen the focus adjustment operation was initiated due to the half-pressof the shutter release button, the camera control unit 21 may send atsuch a time a signal requesting the transmission of the maximum imageplane movement coefficient K_(max) via the camera transceiver unit 29and the lens transceiver unit 38, thereby to acquire it. In this case,the lens control unit 36 may be configured to: receive from the cameracontrol unit 21 the signal requesting the transmission of the maximumimage plane movement coefficient K_(max); use this as the basis to referto the table which is stored in the lens memory 37 and represents therelationship between each lens position and the image plane movementcoefficient K thereby to acquire the maximum image plane movementcoefficient K_(max); and transmit it to the camera control unit 21 viathe lens transceiver unit 38 and the camera transceiver unit 29.

An alternative configuration may also be possible such that the cameracontrol unit 21 acquires the maximum image plane movement coefficientK_(max) also in the case where the lens position of the zoom lens 32varies, because driving the zoom lens 32 may cause the lens position ofthe zoom lens 32 to vary and therefore cause the maximum image planemovement coefficient K_(max) to be different.

Then at step S302, like at the above-described step S202 shown in FIG.10, the camera control unit 21 performs acquisition of informationregarding the play amount G (see FIG. 8) of the drive transmissionmechanism for the focus lens 33.

Then at step S303, the camera control unit 21 calculates an image planemovement amount I_(G) corresponding to the play amount G on the basis ofthe above-described maximum image plane movement coefficient K_(max)acquired at step S301 and the above-described information regarding theplay amount G of the drive transmission mechanism for the focus lens 33acquired at step S302. The image plane movement amount I_(G)corresponding to the play amount G is a movement amount of the imageplane when the focus lens is driven exactly by the same amount as theplay amount G, and can be calculated in accordance with Expression (3)below in the present embodiment.(Image plane movement amount I _(G) corresponding to play amountG)=(Play amount G)×(Maximum image plane movement coefficient K_(max))  (3)

Then at step S304, like at the above-described step S204 shown in FIG.10, the camera control unit 21 performs a process of comparing theabove-described image plane movement amount I_(G) corresponding to theplay amount G calculated at step S303 with a predetermined image planemovement amount I_(P), and the result of this comparison is used to makea determination whether the image plane movement amount I_(G)corresponding to the play amount G is not larger than the predeterminedimage plane movement amount I_(P), i.e., whether a condition of (Imageplane movement amount I_(G) corresponding to play amountG)≦(Predetermined image plane movement amount I_(P)) is satisfied ornot. The predetermined image plane movement amount I_(P) may be set inthe same way as the above-described second embodiment.

At step S305, it has been determined at the above-described step S304that the image plane movement amount I_(G) corresponding to the playamount G is not larger than the predetermined image plane movementamount I_(P), in which case, like at the above-described step S205 shownin FIG. 10, it is determined that the lens position of the focus lens 33after the drive can fall within the focal depth of the optical systemeven without the drive for reducing play and that the drive for reducingplay is not to be performed at the time of focusing drive, and suchdetermination is used as the basis to perform the focusing drive withoutthe drive for reducing play.

At step S306, on the other hand, it has been determined at theabove-described step S304 that the image plane movement amount I_(G)corresponding to the play amount G is larger than the predeterminedimage plane movement amount I_(P), in which case, like at theabove-described step S206 shown in FIG. 10, it is determined that thelens position of the focus lens 33 after the drive cannot fall withinthe focal depth of the optical system if the drive for reducing play isnot performed and that the drive for reducing play is to be performed atthe time of focusing drive, and such determination is used as the basisto perform the focusing drive along with the drive for reducing play.

According to the third embodiment, advantageous effects can be obtainedin addition to those in the above-described second embodiment.

That is, the third embodiment can prevent effectively that, even whenthe drive for reducing play is actually necessary, the drive forreducing play may nevertheless be determined to be unnecessary dependingon the lens position of the focus lens 33, because the maximum imageplane movement coefficient K_(max), which is set for each lens positionof the zoom lens 32, is used in the third embodiment to calculate theimage plane movement amount I_(G) corresponding to the play amount G ofthe drive transmission mechanism for the focus lens 33, so that it ispossible to determine whether or not the drive for reducing play at thetime of focusing is necessary regardless of the lens position of thefocus lens 33. In particular, if a lens barrel is used which has acharacteristic that the image plane movement coefficient K significantlyvaries despite the same lens position of the zoom lens 32 when the lensposition of the focus lens 33 varies, then, even when the drive forreducing play is actually necessary, the possibility that the drive forreducing play is determined to be unnecessary is high, so in such a casethe present embodiment is particularly effective.

Thus, depending on the types of lens barrels, due to their structure,the ratio of the change in the image plane movement coefficient K to thechange in the lens position of the focus lens 33 is considered to bedifferent. In this regard, a modified embodiment may be configured suchthat, for example, when the lens barrel 3 is attached to the camera body2, a determination is made whether the ratio of the change in the imageplane movement coefficient K to the change in the lens position of thefocus lens 33 is not smaller than a predetermined threshold, and if notsmaller than the predetermined threshold, then the maximum image planemovement coefficient K_(max) is used like in the third embodiment, whileif smaller than the predetermined threshold, then the current positionimage plane movement coefficient K_(cur) is used like in the secondembodiment, thus appropriately performing such selection.

Fourth Embodiment

A fourth embodiment according to the present invention will then bedescribed. The fourth embodiment has the same configuration as that ofthe above-described second embodiment except that the camera 1 shown inFIG. 1 operates as will be described below.

The above-described second embodiment has been exemplified in which theimage plane movement amount I_(G) corresponding to the play amount G iscalculated using the current position image plane movement coefficientK_(cur) that corresponds to the lens position of the zoom lens 32 andthe lens position of the focus lens 33 at the time of initiating thereverse drive after completing the scan operation for the focus lens 33when calculating the image plane movement amount I_(G) corresponding tothe play amount G. In contrast, according to the fourth embodiment, assubstitute for the current position image plane movement coefficientK_(cur), the image plane movement coefficient K that corresponds to thelens position of the focus lens 33 when located in the vicinity of thefocused position is acquired as a focusing vicinity image plane movementcoefficient K_(fou), which is used to calculate the image plane movementamount I_(G) corresponding to the play amount G, thus in this regard thefourth embodiment differs from the above-described second embodiment.

An example of operation according to the fourth embodiment will now bedescribed with reference to the flowchart shown in FIG. 12. Like in theabove-described second embodiment, the operation below is executed ifthe focused position was detected using the contrast detection system atstep S109 in the above-described flowchart shown in FIG. 7.

More specifically, if the focused position is detected using thecontrast detection system, then the camera control unit 21 performs atstep S401 a process of acquiring the image plane movement coefficient Kthat corresponds to the lens position of the focus lens 33 when locatedin the vicinity of the focused position as a focusing vicinity imageplane movement coefficient K_(fou). The method of acquiring the focusingvicinity image plane movement coefficient K_(fou) may be as follows, forexample. That is, while executing the scan operation for the focus lens33, the camera control unit 21 stores sequentially the image planemovement coefficient K corresponding to the current lens position, whichis acquired using the stationary communication between the cameracontrol unit 21 and the lens control unit 36, along with informationregarding the lens position of the focus lens 33. When the focusedposition is then detected, the image plane movement coefficient K whenthe focus lens 33 was located in the vicinity of the focused position isread out, which can be used as the focusing vicinity image planemovement coefficient K_(fou).

Then at step S402, like at the above-described step S202 shown in FIG.10, the camera control unit 21 performs acquisition of informationregarding the play amount G (see FIG. 8) of the drive transmissionmechanism for the focus lens 33.

Then at step S403, the camera control unit 21 calculates an image planemovement amount I_(G) corresponding to the play amount G on the basis ofthe above-described focusing vicinity image plane movement coefficientK_(fou) acquired at step S401 and the above-described informationregarding the play amount G of the drive transmission mechanism for thefocus lens 33 acquired at step S402. The image plane movement amountI_(G) corresponding to the play amount G is a movement amount of theimage plane when the focus lens is driven exactly by the same amount asthe play amount G, and can be calculated in accordance with Expression(4) below in the present embodiment.(Image plane movement amount I _(G) corresponding to play amountG)=(Play amount G)×(Focusing vicinity image plane movement coefficient K_(fou))  (4)

Then at step S404, like at the above-described step S204 shown in FIG.10, the camera control unit 21 performs a process of comparing theabove-described image plane movement amount I_(G) corresponding to theplay amount G calculated at step S403 with a predetermined image planemovement amount I_(P), and the result of this comparison is used to makea determination whether the image plane movement amount I_(G)corresponding to the play amount G is not larger than the predeterminedimage plane movement amount I_(P), i.e., whether a condition of (Imageplane movement amount I_(G) corresponding to play amountG)≦(Predetermined image plane movement amount I_(P)) is satisfied ornot. The predetermined image plane movement amount I_(P) may be set inthe same way as the above-described second embodiment.

At step S405, it has been determined at the above-described step S404that the image plane movement amount I_(G) corresponding to the playamount G is not larger than the predetermined image plane movementamount I_(P), in which case, like at the above-described step S205 shownin FIG. 10, it is determined that the lens position of the focus lens 33after the drive can fall within the focal depth of the optical systemeven without the drive for reducing play and that the drive for reducingplay is not to be performed at the time of focusing drive, and suchdetermination is used as the basis to perform the focusing drive withoutthe drive for reducing play.

At step S406, on the other hand, it has been determined at theabove-described step S404 that the image plane movement amount I_(G)corresponding to the play amount G is larger than the predeterminedimage plane movement amount I_(P), in which case, like at theabove-described step S206 shown in FIG. 10, it is determined that thelens position of the focus lens 33 after the drive cannot fall withinthe focal depth of the optical system if the drive for reducing play isnot performed and that the drive for reducing play is to be performed atthe time of focusing drive, and such determination is used as the basisto perform the focusing drive along with the drive for reducing play.

According to the fourth embodiment, advantageous effects can be obtainedin addition to those in the above-described second embodiment.

That is, according to the fourth embodiment, when calculating the imageplane movement amount I_(G) corresponding to the play amount G of thedrive transmission mechanism for the focus lens 33, the focusingvicinity image plane movement coefficient K_(fou) is used which is theimage plane movement coefficient that corresponds to the lens positionof the focus lens 33 when located in the vicinity of the focusedposition, in which case the calculated image plane movement amount I_(G)corresponding to the play amount G can be based on the image planemovement coefficient when the focus lens 33 was actually driven to thefocused position. Accordingly, the fourth embodiment can calculate theimage plane movement amount I_(G) corresponding to the play amount Gwith higher accuracy, and it is thereby possible to furtherappropriately make a determination whether the drive for reducing playis necessary or not.

Fifth Embodiment

A fifth embodiment according to the present invention will then bedescribed. In the fifth embodiment, the description of a similarconfiguration to that of the above-described first embodiment will beomitted.

The operation according to the fifth embodiment described below can beexecuted in combination with any of those according to theabove-described first to fourth embodiments, or solely executedseparately from those according to the first to fourth embodiments.

Single-lens reflex digital camera 1 a according to the fifth embodiment,as shown in FIG. 13, comprises a camera body 2 a, a mirror system 240, aphase difference AF module 210 and a finder optical system, and in thisregard it has a different configuration from that of the above-describedcamera 1.

The mirror system 240 comprises: a quick return mirror 241 that movespivotally around a pivot axis 243 within a predetermined angular rangebetween an observing position and an imaging position to an object; anda sub mirror 242 that is supported pivotally at the quick return mirror241 and moves pivotally in synchronization with the pivotal movement ofthe quick return mirror 241. In FIG. 13, a state where the mirror system240 is located at the observing position to an object is indicated bysolid lines, while a state where the mirror system 240 is located at theimaging position to an object is indicated by two-dot chain lines.

The quick return mirror 241 is configured of a half mirror and, in astate of being at the observing position to an object, reflects part oflight beams (optical axes L3 and L4) of those from an object (opticalaxis L1) to guide them to the finder 135 and the photometric sensor 137while transmitting the remaining light beams (optical axis L5) to guidethem to the sub mirror 242. In contrast, the sub mirror 242 isconfigured of a total reflection mirror and guides the light beams(optical axis L4) transmitted through the quick return mirror 241 to thephase difference AF module 210.

The light beams from an object reflected by the quick return mirror 241form an image on a focusing screen 231 arranged at a plane opticallyequivalent to an imaging device 22 a, thereby being observable via apentaprism 233 and an ocular lens 234. At this time, a transmissive-typeliquid crystal display device 232 superimposes indications such as afocus detection area mark onto the image of an object projected on thefocal plane plate 131 to display them.

The operating unit 28 has a live-view imaging ON/OFF switch (not shown).When the live-view imaging is turned OFF and the mirror system 240 is ina state of being at the observing position to an object, the phasedifference AF can be performed using the phase difference AF module 210.In addition, if the live-view imaging is turned ON, then the mirrorsystem 240 comes at the imaging position to an object and a state isobtained in which the light beams from an object are guided to theimaging device 22 a (such as a state where a through image isdisplayed), so that the contrast AF can be performed. In this case, asimilar operation to those in the above first to fourth embodiments canbe performed. Examples of the operation according to the fifthembodiment will then be described in detail with reference to FIGS. 14,15 and 16.

The operation shown in FIG. 14 is initiated by the power of the camera 1a being turned on. First at step S501, the camera body 2 a performscommunication for identifying a lens barrel 3. This is because theavailable communication format is different depending on the types oflens barrels.

Then at step S502, a determination is made whether or not the live-viewimaging ON/OFF switch provided at the operating unit 28 was operated bythe photographer, and if the live-view imaging is turned ON, then themirror system 240 comes at the imaging position to an object, so thatthe light beams from an object are guided to the imaging device 22 a.

At step S503, the stationary communication is initiated between thecamera body 2 a and the lens barrel 3. In the stationary communication,the lens control unit 36, when receiving the first request signal fromthe camera control unit 21, repeatedly transmits lens information suchas the current position image plane movement coefficient K_(cur) to thecamera control unit 21. The stationary communication is repeatedlyperformed at step S503 and at subsequent steps. It is preferred that thestationary communication is performed repeatedly until the power switchis turned off, for example.

At step S504, a determination is made whether or not a certain operationwas performed by the photographer, such as a half-press operation of therelease button provided at the operating unit 28 (first switch SW1turned on) or an AF initiating operation, and if such an operation wasperformed, then the routine proceeds to step S505 (a case of thehalf-press operation being done will hereinafter be described indetail).

At step S505, the camera control unit 21 is triggered by the half-press(first switch SW1 turned on) operation by the photographer to transmitthe second request signal to the lens control unit 36. Conditions fortransmitting the second request signal to the lens control unit 36 mayinclude a case where the photographer performs the AF initiatingoperation, a case where the half-press of the shutter release buttoninitiates the focus adjustment operation, a case where the photographerperforms an operation for driving the zoom lens 32, and a case where thepower of the camera 1 a is turned on.

At step S506, after receiving the second request signal, the lenscontrol unit 36 refers to the table (see FIG. 6), which is stored in thelens memory 37 and represents the relationship between each lensposition and the image plane movement coefficient K, to acquire amaximum image plane movement coefficient K_(max) and a minimum imageplane movement coefficient K_(min) that correspond to the current lensposition of the zoom lens 32, and transmits the maximum image planemovement coefficient K_(max) and the minimum image plane movementcoefficient K_(min) to the camera control unit 21.

At step S507, the camera control unit 21 transmits a scan drive command(instruction to initiate scan drive) to the lens control unit 36 inorder to perform the focus detection using the contrast detectionsystem. The scan drive command to the lens control unit 36 (instructionof drive speed for scan drive or instruction of drive position) may begiven as the drive speed for the focus lens 33, the image plane movementspeed, or the target drive position, etc. Then at step S508, the lenscontrol unit 36 performs the drive control for the focus lens 33 on thebasis of the scan drive command.

Then at step S509, the camera control unit 21 performs an abnormalitydetermination process as will be described later. At step S510, thecamera control unit 21 determines whether or not a peak value of thefocus evaluation value was able to be detected (whether a focusedposition was able to be detected or not). If a peak value of the focusevaluation value was not able to be detected, the routine returns tostep S508, whereas if a peak value of the focus evaluation value wasable to be detected, the routine proceeds to step S511.

At step S511, the camera control unit 21 transmits to the lens controlunit 36 a command for performing the focusing drive to the positioncorresponding to the peak value of the focus evaluation value. The lenscontrol unit 36 performs the drive control for the focus lens 33 inresponse to the received command.

At step S512, the camera control unit 21 makes a determination that thefocus lens 33 has reached the position corresponding to the peak valueof the focus evaluation value, and performs the imaging control for astill image if the full-press operation (second switch SW2 turned on)was performed by the photographer. After completing the imaging control,the routine returns again to step S503.

The abnormality determination process (see step S509 in FIG. 14) willthen be described in detail with reference to FIGS. 15 and 16.

The description now refers to FIG. 15. At step S601, a determination ismade whether or not the current position image plane movementcoefficient K_(cur) acquired repeatedly via the stationary communicationis larger than the above-described maximum image plane movementcoefficient K_(max) acquired at step S506. That is, it is determinedwhether or not there was detected a current position image planemovement coefficient K_(cur) satisfying a condition of (Maximum imageplane movement coefficient K_(max))<(Current position image planemovement coefficient K_(cur)). If a current position image planemovement coefficient K_(cur) satisfying the condition of (Maximum imageplane movement coefficient K_(max))<(Current position image planemovement coefficient K_(cur)) was detected, then some abnormality isconsidered to occur, such as communication abnormality between thecamera body 2 and the lens barrel 3, and the routine proceeds to stepS605 at which an abnormality flag is set “1” to exit the abnormalitydetermination process, followed by step S510 shown in FIG. 14. Note thatthe abnormality flag is set “0” in a normal condition such as when noabnormality occurs. If, on the other hand, a current position imageplane movement coefficient K_(cur) satisfying the condition of (Maximumimage plane movement coefficient K_(max))<(Current position image planemovement coefficient K_(cur)) is not detected, then the routine proceedsto step S602.

At step S602, a determination is made whether or not the focus lens 33was driven from the near end to the infinite end while from the timewhen the power of the camera 1 was turned on to the present time. If thefocus lens 33 was driven from the near end to the infinite end, then theroutine proceeds to step S606 at which a determination is made whetheror not, as a result of driving the focus lens 33 from the near end tothe infinite end, a current position image plane movement coefficientK_(cur) satisfying a condition of (Current position image plane movementcoefficient K_(cur))=(Maximum image plane movement coefficient K_(max))was able to be detected among those obtained via the stationarycommunication. If, despite the focus lens 33 driven from the near end tothe infinite end, a current position image plane movement coefficientK_(cur) satisfying the condition of (Current position image planemovement coefficient K_(cur))=(Maximum image plane movement coefficientK_(max)) was not able to be detected, then some abnormality isconsidered to occur, such as communication abnormality between thecamera body 2 and the lens barrel 3, and the routine proceeds to stepS607 at which the abnormality flag is set “2” to exit the abnormalitydetermination process, followed by step S510 shown in FIG. 14. If, atstep S606, a current position image plane movement coefficient K_(cur)satisfying the condition of (Current position image plane movementcoefficient K_(cur))=(Maximum image plane movement coefficient K_(max))was able to be detected, then the routine exits the abnormalitydetermination process and proceeds to step S510 shown in FIG. 14.

If, at step S602, the focus lens 33 was determined not to be driven fromthe near end to the infinite end, then the routine proceeds to stepS603.

Then at step S603, the camera control unit 21 determines whether thedrive operation for the zoom lens 32 was performed or not. If the driveoperation for the zoom lens 32 was determined to be performed, theroutine proceeds to step S604, whereas if the drive operation for thezoom lens 32 was determined not to be performed, the routine exits theabnormality determination process and proceeds to step S510 shown inFIG. 14.

At step S604, the camera control unit 21 transmits again the secondrequest signal to the lens control unit 36, which then returns to thecamera control unit 21 a maximum image plane movement coefficientK_(max) that corresponds to the lens position of the zoom lens 32 afterit was driven. In addition, the camera control unit 21 resets themaximum image plane movement coefficient K_(max) and the currentposition image plane movement coefficient K_(cur) which were obtainedbefore driving the zoom lens 32.

This is because the above-described determinations at steps S601 andS606 are to compare the maximum image plane movement coefficient K_(max)and the current position image plane movement coefficient K_(cur) whichwere obtained when the zoom lens 32 was at the same lens position, so ifthe lens position of the zoom lens 32 varies, then the above-describeddeterminations at steps S601 and S606 cannot appropriately be performedunless the maximum image plane movement coefficient K_(max) and thecurrent position image plane movement coefficient K_(cur) are newlycollected. After completing the process at step S604, the routinereturns to step S601.

With reference to FIG. 16, a case where the abnormality flag is set “1”will then be described in detail. The description with reference to FIG.16 will be directed to an example of the case where the position of thezoom lens (focal distance) is at “f1” (see FIG. 6).

FIG. 16 exemplifies a case where the half-press operation of the shutterrelease button was performed at time t2 by the photographer, in whichcase it is assumed that the lens control unit 36 transmits at time t4 tothe camera control unit 21 the maximum image plane movement coefficientK_(max) of “K12” rather than “K11”. The camera control unit 21 thensends at time t7 the scan drive command to the lens control unit 36. Attime t1, t3, t5, t6 before the scan drive command, the maximum imageplane movement coefficient K_(max) is “K19” because the focus lens 33 isnot moved.

After time t8 at which the scan drive command has been sent, the currentposition image plane movement coefficient K_(cur) is “K18” at time t9,then “K12” at time t10, then “K11” at time t12.

In this case, the example shown in FIG. 16 is such that the cameracontrol unit 21 receives at time t4 the maximum image plane movementcoefficient K_(max) of “K12”. Therefore, at time t12, the currentposition image plane movement coefficient K_(cur) of “K11” larger than“K12” is received, which satisfies the condition of (Maximum image planemovement coefficient K_(max))<(Current position image plane movementcoefficient K_(cur)) (see step S601 shown in FIG. 15), so that theabnormality flag is set “1” (see step S605 shown in FIG. 15).

In the above-described embodiment, if the abnormality flag was set “1”at step S605 (if a current position image plane movement coefficientK_(cur) satisfying the condition of (Maximum image plane movementcoefficient K_(max))<(Current position image plane movement coefficientK_(cur)) was detected), or if the abnormality flag was set “2” at stepS606 (if, despite the focus lens 33 driven from the near end to theinfinite end, a current position image plane movement coefficientK_(cur) satisfying the condition of (Current position image planemovement coefficient K_(cur))=(Maximum image plane movement coefficientK_(max)) was not able to be detected), then some abnormality isconsidered to occur, such as communication abnormality between thecamera body 2 and the lens barrel 3.

If the abnormality flag was set “1” or “2”, it is preferred to perform aprocess for abnormality. The process for abnormality may preferablyinclude prohibiting display of focused state such as using theelectronic viewfinder 26, for example. If the abnormality flag was set“1” or “2”, then abnormalities such as communication abnormality,circuit abnormality and power abnormality may possibly occur, so thereliability in AF cannot be ensured. For this reason, it is preferred toperform the process for abnormality, such as prohibiting display offocused state, for the purpose of avoiding “display of focused state”with low reliability. Note that, if at step S509 the abnormality flag isset “1” or “2” and display of focused state is inhibited, then displayof focused state is not to be performed even when the focus lens 33reaches the focused position at step S511.

If the abnormality flag was set “1” or “2”, then, alternatively or inaddition to performing the process of prohibiting display of focusedstate, it is also preferred to perform a whole range search that drivesthe focus lens 33 from the near end to the infinite end, for example. Byperforming the whole range search, causes for the abnormality may beconfirmed to disappear.

It is further preferred to perform the whole range search such that thefocus lens 33 is driven from the near end to the infinite end using asecond drive speed that is sufficiently lower than a first drive speedas the normal drive speed. This is because a sufficiently low seconddrive speed allows the whole range search to be performed safely. Thisis also because, if the drive speed for the focus lens 33 was too highto detect a current position image plane movement coefficient K_(cur)satisfying the condition of (Current position image plane movementcoefficient K_(cur))=(Maximum image plane movement coefficient K_(max))then the whole range search using a sufficiently low second drive speedmay allow detecting such a current position image plane movementcoefficient K_(cur).

If the abnormality flag was set “1” or “2”, then, alternatively or inaddition to the process of prohibiting display of focused state and/orthe process of performing the whole range search using a sufficientlylow second speed, a further process may be performed such as forprohibiting both the focus detection using the phase differencedetection system and the focus detection using the contrast detectionsystem. In particular, if the abnormality flag is set “1” or “2” so thatsome abnormality such as communication abnormality is considered tooccur, then the possibility that a successful focus detection resultcannot be obtained is high even when the focus detection using the phasedifference detection system and the focus detection using the contrastdetection system are performed, and hence, in such a case the focusdetection using the phase difference detection system and the focusdetection using the contrast detection system may be prohibited.

In the fifth embodiment, if the abnormality flag was once set “1” or“2”, then some abnormality such as communication abnormality isconsidered to occur, and it is thus preferred that the abnormality flagremains set “1” or “2” without being reset until the power is turned offor the lens barrel 3 is replaced.

In the fifth embodiment, the reliability in AF cannot be ensured if, forexample, the abnormality flag is set “1” or “2” at step S509 shown inFIG. 14, and hence, to avoid meaningless drive of the focus lens 33, aprocess may be performed to prohibit drive of the focus lens 33regardless of whether or not the camera control unit 21 was able todetect the peak value at step S510. In this case, it is preferred thatthe focus lens 33 is prohibited from being driven until the power isturned off or the lens barrel 3 is replaced.

If the abnormality flag is set “1” or “2” at step S509 shown in FIG. 14,for example, then the camera control unit 21 may perform one or moreadditional processes, such as a process of performing the whole rangesearch using a sufficiently low second drive speed regardless of whetheror not the peak value was able to be detected at step S510, a process ofprohibiting at least one of the focus detection using the phasedifference detection system and the focus detection using the contrastdetection system, a process of turning off the power of the camera, anda process of displaying an alert that some abnormality occurs.

The reliability in AF cannot be ensured if, for example, the abnormalityflag is set “1” or “2” at step S509 shown in FIG. 14, and a furtherprocess may therefore be possible such that the camera control unit 21does not perform the focusing drive at step S511 even when the peakvalue was detected at step S510.

Sixth Embodiment

A sixth embodiment according to the present invention will then bedescribed. In the sixth embodiment, the description of a similarconfiguration to that of the above-described fifth embodiment will beomitted.

The operation according to the sixth embodiment described below can beexecuted in combination with any of those according to theabove-described first to fifth embodiments, or solely executedseparately from those according to the first to fifth embodiments.

In the sixth embodiment shown in FIG. 18, steps S501-S504, S507, S508and S510-S512 are similar to those in FIG. 14, so the detailedexplanation will be omitted. At step S504, a determination is madewhether or not a certain operation was performed, such as a half-pressoperation of the release button (first switch SW1 turned on) or an AFinitiating operation, and if such an operation was performed, then theroutine proceeds to step S507 at which the camera control unit 21transmits a scan drive command to the lens control unit 36, followed bystep S508 at which the lens control unit 36 performs the drive controlfor the focus lens 33 on the basis of the scan drive command.

Then at step S705, the camera control unit 21 is triggered by the scandrive command (see step S507) to the lens control unit 36 toperiodically transmit the second request signal to the lens control unit36. The condition for transmitting the second request signal to the lenscontrol unit 36 may be based on, for example, a trigger at a timing whenthe camera control unit 21 detects that the lens control unit 36actually initiates the drive control for the focus lens 33, or a triggerat a timing when a certain signal is transmitted from the lens controlunit 36 to the camera control unit 21 after the scan drive command, etc.The second request signal may be transmitted concurrently with the scandrive command to the lens control unit 36.

It is preferred in the present embodiment that the camera control unit21 periodically transmits the second request signal until a conditionfor stopping the transmission of the second request signal is satisfiedas will be described later. The period at which the second requestsignal is transmitted may preferably be shorter than the period at whichthe first request signal is transmitted. For example, it may preferablybe half or less the period at which the first request signal istransmitted.

Then at step S706, while periodically receiving the second requestsignal, the lens control unit 36 refers to the table (see FIG. 6), whichis stored in the lens memory 37 and represents the relationship betweeneach lens position and the image plane movement coefficient K, toacquire a maximum image plane movement coefficient K_(max) and a minimumimage plane movement coefficient K_(min) that correspond to the currentlens position of the zoom lens 32, and periodically transmits themaximum image plane movement coefficient K_(max) and the minimum imageplane movement coefficient K_(min) to the camera control unit 21.

Then at step S709, the camera control unit 21 performs an abnormalitydetermination process as will be described later. For example, thecamera control unit 21 can periodically perform the abnormalitydetermination, while periodically transmitting the second requestsignal, using a trigger at a timing when transmitting the second requestsignal or at a timing when receiving the maximum image plane movementcoefficient K_(max) and the minimum image plane movement coefficientK_(min). Transmitting the second request signal at a short period allowsthe abnormality determination to be performed at the short period, and asuccessful abnormal determination can thus be achieved.

Then at step S510, the camera control unit 21 determines whether or nota peak value of the focus evaluation value was able to be detected(whether a focused position was able to be detected or not). If a peakvalue of the focus evaluation value was not able to be detected, theroutine returns to step S508. If a peak value of the focus evaluationvalue was able to be detected, then the routine proceeds to step S511 atwhich the camera control unit 21 stops the periodical transmission ofthe second request signal. The condition for stopping the transmissionof the second request signal may be based on, for example, a trigger ata timing when a command for the focusing drive is transmitted to thelens control unit 36, when the focus lens 33 reaches a position thatcorresponds to the peak value of the focus evaluation value, when thecamera control unit 21 determines that a peak position cannot bedetected, when the camera control unit 21 determines to end the scanoperation, when the camera control unit 21 determines to end thecontrast AF control, or when the camera control unit 21 determines toend the live-view display, etc. It is preferred that the first requestsignal is periodically transmitted from before a time when theperiodical transmission of the second request signal is started to aftera time when the periodical transmission of the second request signal isended. In other words, the time period during which the second requestsignal is periodically transmitted is included in the time period duringwhich the first request signal is periodically transmitted.

The abnormality determination process (see step S709 in FIG. 18) willthen be described in detail with reference to FIG. 19. In FIG. 19, stepsS602-S605 and S607 are similar to those in FIG. 15, so the detailedexplanation will be omitted.

At step S801 shown in FIG. 19, a determination is made whether or notthe current position image plane movement coefficient K_(cur) acquiredrepeatedly via the stationary communication is larger than theabove-described maximum image plane movement coefficient K_(max)acquired at step S706 or smaller than the minimum image plane movementcoefficient K_(min). If a current position image plane movementcoefficient K_(cur) satisfying the condition of (Maximum image planemovement coefficient K_(max))<(Current position image plane movementcoefficient K_(cur)) or (Minimum image plane movement coefficientK_(min))>(Current position image plane movement coefficient K_(cur)) wasdetected, then some abnormality is considered to occur, such ascommunication abnormality between the camera body 2 and the lens barrel3, and the routine proceeds to step S605 at which the abnormality flagis set “1” to exit the abnormality determination process, followed bystep S510 shown in FIG. 18. If, on the other hand, a current positionimage plane movement coefficient K_(cur) satisfying the condition of(Maximum image plane movement coefficient K_(max))<(Current positionimage plane movement coefficient K_(cur)) or (Minimum image planemovement coefficient K_(min))>(Current position image plane movementcoefficient K_(cur)) is not detected, then the routine proceeds to stepS602.

If, at step S602, it was determined that the focus lens 33 was drivenfrom the near end to the infinite end, then the routine proceeds to stepS806. At step S806, a determination is made whether or not, as a resultof driving the focus lens 33 from the near end to the infinite end, acurrent position image plane movement coefficient K_(cur) satisfying acondition of (Current position image plane movement coefficientK_(cur))=(Maximum image plane movement coefficient K_(max)) and (Currentposition image plane movement coefficient K_(cur)) (Minimum image planemovement coefficient K_(min)) was able to be detected among thoseobtained via the stationary communication. If, despite the focus lens 33driven from the near end to the infinite end, a current position imageplane movement coefficient K_(cur) satisfying the condition of (Currentposition image plane movement coefficient K_(cur))=(Maximum image planemovement coefficient K_(max)) and (Current position image plane movementcoefficient K_(cur))=(Minimum image plane movement coefficient K_(min))was not able to be detected, then some abnormality is considered tooccur, such as communication abnormality between the camera body 2 andthe lens barrel 3, and the routine proceeds to step S607 at which theabnormality flag is set “2” to exit the abnormality determinationprocess, followed by step S510 shown in FIG. 18. If, at step S806, acurrent position image plane movement coefficient K_(cur) satisfying thecondition of (Current position image plane movement coefficientK_(cur))=(Maximum image plane movement coefficient K_(max)) and (Currentposition image plane movement coefficient K_(cur))=(Minimum image planemovement coefficient K_(min)) was able to be detected, then the routineexits the abnormality determination process and proceeds to step S510shown in FIG. 18.

It should be appreciated that the embodiments heretofore explained aredescribed to facilitate understanding of the present invention and arenot described to limit the present invention. Therefore, it is intendedthat the elements disclosed in the above embodiments include all designchanges and equivalents to fall within the technical scope of thepresent invention. In addition, two or more of the above-describedembodiments may appropriately be combined for use.

For example, the above-described embodiments employ the value calculatedby (Movement amount of image plane)/(Drive amount of focus lens 33) asthe image plane movement coefficient K, but the image plane movementcoefficient K may be a value calculated by (Drive amount of focus lens33)/(Movement amount of image plane).

For example, if the value calculated by (Movement amount of imageplane)/(Drive amount of focus lens 33) is employed as the image planemovement coefficient K, then, as the value (absolute value) increases,the movement amount of the image plane when the focus lens is driven bya certain value (e.g. 1 mm) increases. If the value calculated by (Driveamount of focus lens 33)/(Movement amount of image plane) is employed asthe image plane movement coefficient K, then, as the value (absolutevalue) increases, the movement amount of the image plane when the focuslens is driven by a certain value (e.g. 1 mm) decreases.

According to the above-described embodiments, if, at step S601 shown inFIG. 15, a current position image plane movement coefficient K_(cur)satisfying the condition of (Maximum image plane movement coefficientK_(max))<(Current position image plane movement coefficient K_(cur)) wasdetected, then some abnormality is considered to occur, such ascommunication abnormality between the camera body 2 and the lens barrel3, and the abnormality flag is accordingly set “1” (step S605), while onthe other hand, if a current position image plane movement coefficientK_(cur) satisfying the condition of (Maximum image plane movementcoefficient K_(max))<(Current position image plane movement coefficientK_(cur)) is not detected, then the abnormality flag is set “0” (theroutine proceeds to step S602), but the present invention is not limitedto the above.

For example, the above procedure may be modified such that, if, at stepS601 shown in FIG. 15, a current position image plane movementcoefficient K_(cur) satisfying the condition of (Minimum image planemovement coefficient K_(min))>(Current position image plane movementcoefficient K_(cur)) was detected, then some abnormality is consideredto occur, such as communication abnormality between the camera body 2and the lens barrel 3, and the abnormality flag is accordingly set “1”(step S605), while on the other hand, if a current position image planemovement coefficient K_(cur) satisfying the condition of (Minimum imageplane movement coefficient K_(min))>(Current position image planemovement coefficient K_(cur)) is not detected, then the abnormality flagis set “0” (the routine proceeds to step S602).

According to the above-described embodiments, despite the focus lens 33driven from the near end to the infinite end, if, at step S606 shown inFIG. 15, a current position image plane movement coefficient K_(cur)satisfying the condition of (Current position image plane movementcoefficient K_(cur))=(Maximum image plane movement coefficient K_(max))was not able to be detected, then some abnormality is considered tooccur, such as communication abnormality between the camera body 2 andthe lens barrel 3, and the abnormality flag is accordingly set “2” (stepS607), while on the other hand, if a current position image planemovement coefficient K_(cur) satisfying the condition of (Currentposition image plane movement coefficient K_(cur))=(Maximum image planemovement coefficient K_(max)) was able to be detected, then theabnormality flag is set “0” (the routine exits the abnormalitydetermination process), but the present invention is not limited to theabove.

For example, the above procedure may be modified such that, despite thefocus lens 33 driven from the near end to the infinite end, if, at stepS606 shown in FIG. 15, a current position image plane movementcoefficient K_(cur) satisfying the condition of (Current position imageplane movement coefficient K_(cur))=(Minimum image plane movementcoefficient K_(min)) was not able to be detected, then some abnormalityis considered to occur, such as communication abnormality between thecamera body 2 and the lens barrel 3, and the abnormality flag isaccordingly set “2” (step S607), while on the other hand, if a currentposition image plane movement coefficient K_(cur) satisfying thecondition of (Current position image plane movement coefficientK_(cur))=(Minimum image plane movement coefficient K_(min)) was able tobe detected, then the abnormality flag is set “0” (the routine exits theabnormality determination process).

According to the above-described embodiments, abnormalities such ascommunication abnormality can be detected by a simple process using atleast one of the minimum image plane movement coefficient K_(min) andthe maximum image plane movement coefficient K_(max) thereby to resultin a considerably advantageous effect that a focus adjustment controlapparatus can be provided with high reliability.

The above-described embodiments are configured such that the lens memory37 stores the table which is shown in FIG. 6 and represents therelationship between each lens position and the image plane movementcoefficient K, but a modified configuration may also be possible suchthat the lens control unit 36 rather than the lens memory 37 stores thetable. The above-described embodiments are configured to store the tablewhich is shown in FIG. 6 and represents the relationship between thelens position of the zoom lens 32 and the lens position of the focuslens 33, and the image plane movement coefficient K, but may be modifiedto use a table which represents the relationship between the lensposition only of the zoom lens 32 and the image plane movementcoefficient K, or a table which represents the relationship between thelens position only of the focus lens 33 and the image plane movementcoefficient K. In particular, depending on the type, some lens barrels 3are such that, if the lens position of the zoom lens 32 is the same, thevariation in the image plane movement coefficient K is very small evenwhen the lens position of the focus lens 33 varies, and in such a caseit may be useful to use a table which represents the relationshipbetween the lens position only of the zoom lens 32 and the image planemovement coefficient K. If the lens barrel 3 consists essentially of asingle focus lens, it may be useful to use a table which represents therelationship between the lens position only of the focus lens 33 and theimage plane movement coefficient K.

The above-described embodiments are configured to store the table whichrepresents the relationship between the lens position of the zoom lens32 and the lens position of the focus lens 33, and the image planemovement coefficient K, but may further comprise a table that storesadditional data with consideration for ambient temperature and attitudeof the camera 1.

The above-described embodiments are configured such that the lenscontrol unit 36 transmits the maximum image plane movement coefficientK_(max) and the minimum image plane movement coefficient K_(min) inresponse to the request signal from the camera control unit 21, but thepresent invention is not limited to such a configuration. An alternativeembodiment may be configured, for example, such that the lens controlunit 36 transmits the maximum image plane movement coefficient K_(max)and the minimum image plane movement coefficient K_(min) such as whenreceiving from the camera control unit 21 a signal for driving the zoomlens 32, when receiving from the camera control unit 21 a signal thatnotifies that the shutter release button was half pressed, or whenreceiving from the camera control unit 21 a signal that notifies thatthe focus adjustment operation was initiated due to the half-press ofthe shutter release button, rather than in response to the requestsignal from the camera control unit 21. In a further embodiment, thelens control unit 36 may be configured to transmit either one of themaximum image plane movement coefficient K_(max) or the minimum imageplane movement coefficient K_(min) that represents a minimum value amongthe image plane movement coefficients K set for respective lenspositions of the zoom lens 32, in which case the lens control unit 36may perform the transmission in response to the transmission request ofthe maximum image plane movement coefficient K_(max) or the minimumimage plane movement coefficient K_(min) from the camera control unit21, or the lens control unit 36 may also perform the transmission suchas when receiving a signal for driving the zoom lens 32 even without thetransmission request as in the above.

In the above-described second to fourth embodiments, a scheme of drivefor reducing play has been described such that, when performing thefocusing drive for the focus lens 33, the focus lens 33 is caused toonce pass through the focused position and then driven reversely to thefocused position, but another scheme of drive for reducing play may alsobe employed in which, when performing the focusing drive, a play amountis added to the drive amount required for driving the focus lens 33 tothe focused position. In this case, if the drive for reducing play isnot performed, the focus lens 33 may be driven to the focused positionwithout addition of a play amount.

The camera 1 according to the above-described embodiments is notparticularly limited, and the present invention may for example beapplied to a digital video camera, a built-in lens type digital camera,a camera for mobile phones, a scope, a field scope, or other opticaldevices.

The present invention is not limited to those capable of storing theimage plane movement coefficient K in the lens memory 37 so long as themaximum image plane movement coefficient K_(max) can be transmitted. Forexample, the maximum image plane movement coefficient K_(max) may becalculated such as using the zoom lens position, and the calculatedmaximum image plane movement coefficient K_(max) may be transmitted tothe camera body 2. In a similar manner, the minimum image plane movementcoefficient K_(min) may be calculated such as using the zoom lensposition, and the calculated minimum image plane movement coefficientK_(min) may be transmitted to the camera body 2.

It is also preferred that, if the maximum image plane movementcoefficient K_(max) or the minimum image plane movement coefficientK_(min) varies even though the position of the zoom lens does not vary,for example, then it is determined that an abnormality occurs, and anappropriate process may be performed like in the case where theabnormality flag is set “1” or “2” as shown in FIG. 15.

The maximum image plane movement coefficient K_(max) stored in the lensmemory 37 may also be those shown in FIG. 17. The minimum image planemovement coefficient K_(min) may also be configured in a similar mannerto that for the maximum image plane movement coefficient K_(max), butdetailed illustration is omitted.

The maximum image plane movement coefficient K_(max) and the minimumimage plane movement coefficient K_(min) stored in the lens memory 37may each be an integer, a value including a fraction after the decimalpoint, an index number, or a logarithmic number. The maximum image planemovement coefficient K_(max) and the minimum image plane movementcoefficient K_(min) may each be a decimal number or a binary number,etc.

The present invention is not limited to those in which the electricalcontacts of the mount unit 401 of the camera body 2 and the electricalcontacts of the mount unit 402 of the lens barrel 3 are connected withone another, so long as the maximum image plane movement coefficientK_(max) can be transmitted to the camera body 2. For example, themaximum image plane movement coefficient K_(max) may be transmittedusing a wireless communication line from the lens barrel 3 to the camerabody 2.

-   1 . . . Digital camera-   2 . . . Camera body-   21 . . . Camera control unit-   22 . . . Imaging device-   221 . . . Imaging pixels-   222 a, 222 b . . . Focus detection pixels-   3 . . . Lens barrel-   32 . . . Zoom lens-   33 . . . Focus lens-   36 . . . Lens control unit-   37 . . . Lens memory

What is claimed is:
 1. A lens barrel comprising: an optical system thatincludes a focus adjustment lens; a drive unit that drives the focusadjustment lens in an optical axis direction; a zoom lens drive unitthat drives a zoom lens in the optical axis direction; a transceiverunit that performs transmission and reception of a signal between thelens barrel and a camera body; and a control unit that controls thetransceiver unit so that the transceiver unit transmits to the camerabody a first image plane movement coefficient determined depending on alens position of the focus adjustment lens, wherein the control unit,when receiving a first signal from the camera body via the transceiverunit, transmits to the camera body via the transceiver unit a secondimage plane movement coefficient that does not depend on the lensposition of the focus adjustment lens, wherein when a focal distance ofthe zoom lens does not vary, the second image plane movement coefficientdoes not vary even if the lens position of the focus adjustment lensvaries, but when a focal distance of the zoom lens varies, the secondimage plane movement coefficient varies.
 2. The lens barrel as recitedin claim 1, wherein the second image plane movement coefficient is atleast one of a maximum value and a minimum value of the first imageplane movement coefficient.
 3. A camera body comprising: a focusdetection unit that calculates an evaluation value with regard tocontrast of an image via an optical system to detect a focus adjustmentstate of the optical system; a transceiver unit that performstransmission and reception of a signal between the camera body and alens barrel; and a control unit that uses the signal received via thetransceiver unit to perform drive control for a focus adjustment lensincluded in the optical system, wherein the control unit controls thetransceiver unit so that the transceiver unit transmits to the lensbarrel a first request signal that requests a first image plane movementcoefficient determined depending on a lens position of the focusadjustment lens and a second request signal that requests a second imageplane movement coefficient determined not depending on the lens positionof the focus adjustment lens, and receives the first image planemovement coefficient and the second image plane movement coefficientfrom the lens barrel, the second image plane movement coefficient is atleast one of a maximum value and a minimum value of the first imageplane movement coefficient, and when a movement amount in an opticalaxis direction of the focus adjustment lens is T_(L) and a movementamount of an image plane is T_(I), an image plane movement coefficientis a coefficient that corresponds to a ratio defined by T_(L) and T_(I),and the control unit performs a predetermined operation when the imageplane movement coefficient is a coefficient that corresponds toT_(I)/T_(L) and the first image plane movement coefficient correspondingto a current lens position of the focus adjustment lens is determined tobe larger than the second image plane movement coefficient or when theimage plane movement coefficient is a coefficient that corresponds toT_(L)/T_(I) and the first image plane movement coefficient correspondingto a current lens position of the focus adjustment lens is determined tobe smaller than the second image plane movement coefficient.
 4. Thecamera body as recited in claim 3, wherein the predetermined operationis at least one of control that performs search drive of the focusadjustment lens at a second speed lower than a first speed that is asearch drive speed before the determination, control that prohibitsnotification to a photographer that a focused state is obtained, andcontrol that prohibits the focus detection unit from detecting the focusadjustment state.
 5. A camera system comprising the camera body asrecited in claim 3 and the lens barrel.
 6. A camera body comprising: afocus detection unit that calculates an evaluation value with regard tocontrast of an image via an optical system to detect a focus adjustmentstate of the optical system; a transceiver unit that performstransmission and reception of a signal between the camera body and alens barrel; and a control unit that uses the signal received via thetransceiver unit to perform drive control for a focus adjustment lensincluded in the optical system, wherein the control unit controls thetransceiver unit so that the transceiver unit transmits to the lensbarrel a first request signal that requests a first image plane movementcoefficient determined depending on a lens position of the focusadjustment lens and a second request signal that requests a second imageplane movement coefficient determined not depending on the lens positionof the focus adjustment lens, and receives the first image planemovement coefficient and the second image plane movement coefficientfrom the lens barrel, the second image plane movement coefficient is atleast one of a maximum value and a minimum value of the first imageplane movement coefficient, and the control unit performs apredetermined operation when the first image plane movement coefficientequal to the second image plane movement coefficient is not detected asa result of acquiring the first image plane movement coefficientcorresponding to a current lens position of the focus adjustment lenswhile driving the focus adjustment lens from one end to the other end inan optical axis direction.
 7. The lens barrel as recited in claim 1,wherein the first image plane movement coefficient representscorrespondence relationship between a movement amount of the focusadjustment lens and a movement amount of an image plane.
 8. The lensbarrel as recited in claim 2, wherein the maximum value is a value wherethe movement amount of an image plane with regard to the movement amountof the focus adjustment lens becomes maximum within a driving range ofthe focus adjustment lens driven by the drive unit, and the minimumvalue is a value where the movement amount of the image plane withregard to the movement amount of the focus adjustment lens becomesminimum within the driving range of the focus adjustment lens driven bythe drive unit.
 9. The lens barrel as recited in claim 2, wherein thetransceiver unit transmits, to the camera body, the second image planemovement coefficient after drive of the focus adjustment lens fordetecting a focusing position of the optical system is started.
 10. Thelens barrel as recited in claim 2, wherein the transceiver unitreceives, from the camera body, control information for controlling thedrive by the drive unit, the transceiver unit transmits, to the camerabody, the first image plane movement coefficient, the maximum value andthe minimum value of the first image plane movement coefficient beforereceiving the control information, the drive unit starts the drive ofthe focus adjustment lens for detecting a focusing position of theoptical system based on the control information, and the transceiverunit repeatedly transmits, to the camera body, the first image planemovement coefficient, the maximum value and the minimum value of thefirst image plane movement coefficient while the focus adjustment lensis driven.
 11. The lens barrel as recited in claim 2, wherein the firstimage plane movement coefficient, the maximum value and the minimumvalue of the first image plane movement coefficient are information fordetermining reliability of detection of a focusing position of theoptical system.
 12. The lens barrel as recited in claim 2, wherein thetransceiver unit receives, from the camera body, the first signal and asecond signal different from the first signal, and the transceiver unittransmits the first image plane movement coefficient after receiving thesecond signal, and transmits the maximum value and the minimum value ofthe first image plane movement coefficient after receiving the firstsignal.
 13. The lens barrel as recited in claim 12, wherein thetransceiver unit receives the second signal at a second timing differentfrom a first timing when the first signal is received.